Establishment of gender related 99th percentile values for cardiac troponin-T among young and middle-aged adult Egyptians 

Establishment of gender related 99th percentile values for cardiac troponin-T among young and middle-aged adult Egyptians | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Establishment of gender related 99th percentile values for cardiac troponin-T among young and middle-aged adult Egyptians Ahmed Tork, Mohamed Labib, Abeer Rabea, Abeer Ali This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5299564/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Background Cardiac troponins are the preferred biomarkers for the diagnosis of acute myocardial infarction (AMI). The stable nature of cardiac troponin T (cTnT) in the circulation and the worldwide available single standardized assay make it a more precise biomarker of AMI. The manufacturer’s proposed upper reference limit (URL) for the high sensitive (hs)-cTnT assay does not take into consideration patients’ gender, age or race. The study aimed at establishing and comparing gender-specific upper reference limit for cardiac troponin-T among apparently healthy young adult Egyptians. Subjects and methods 240 adult Egyptians (120 males and 120 females) participated in this study. Serum cTnT was determined using a commercially available hs-cTnT electrochemiluminescent immunoassay. The gender related 99th percentile values were then calculated to represent the URLs for cTnT according to the CLSI and IFCC approved guidelines. Results Serum cTnT was significantly higher in males compared to females (p < 0.001). The 99th percentile URL for cTnT in females (12.58 ng/L) was lower than that of males (19.55 ng/L). Upon dividing them according to an age cutoff value of 36 years, serum cTnT level was significantly lower among those aged < 36 years old (n = 119) compared to those aged 36 years old or more (n = 121) (p < 0.001), with a proposed 99th percentile URL after including outliers of 18.1 ng/L for the former and 16.42 ng/L for the latter, while after excluding outliers the URL was 10.0 ng/L for the former and 12.6 ng/L for the latter. Moreover, a significantly higher serum cTnT value among males compared to females was only noticed in those aged less than 36 years old (p = 0.001). Conclusion: An adult patient in early diagnosis of AMI by increasing both assay’s specificity among adult The use of age and gender specific 99th percentile value as an URL of hs-cTnT assay would benefit males (decreasing over-diagnosis) and assay’s sensitivity among adult females (decreasing under-diagnosis). Acute myocardial infarction high sensitive cTnT 99th percentile URL Figures Figure 1 Figure 2 Introduction Coronary artery disease accounts for 15.9% of all deaths worldwide. Acute myocardial infarction (AMI) is still the first cause of death among women all over the world, where more than 30,000 young women < 55 years of age are hospitalized with AMI every year in the United States alone. The rising incidence of AMI among younger women in recent decades goes hand in hand with the rising incidence of diabetes mellitus, metabolic syndrome, polycystic ovaries and non-traditional risk factors such as anxiety, depression, stress and the use of oral contraceptives pills [ 1 ]. Circulating levels of cardiac troponins (cTn) are nowadays considered the preferred biomarkers in the diagnosis of acute myocardial infarction (AMI). In peripheral blood, after onset of myocardial injury cardiac troponins begin to rise within 3 to 4 hours and remain elevated for 10 to 14 days [ 2 ]. According to the Fourth Universal Definition of Myocardial Infarction published in August 2018; detection of an elevated cTn value above the 99th percentile upper reference limit (URL) is defined as myocardial injury, where injury is considered acute if there is a rise and/or fall of cTn values [ 3 ]. Two types of assays exist for cardiac troponins; cardiac troponin-I (cTnI) and cardiac troponin-T (cTnT) immunoassays. Different available cTnI immunoassays use different capture and detection antibodies that recognize different epitopes of cTnI with different affinities for its various forms in the circulation, whether resulting from post-translational modifications [proteolytic degradation, phosphorylation, oxidation and reduction] or complexing with other molecules [Troponin-C, heparin, heterophile or human antimouse antibodies, and cTnI specific autoantibodies circulating in blood] [ 4 , 5 ]. Moreover, the lack of a commutable reference material that standardize cTnI results makes absolute concentrations of cTnI determined by different immunoassays very inconsistent even for different assays and instruments marketed by the same manufacturer [ 4 ]. On the other hand, the more stable nature of cTnT molecule in circulation and the worldwide availability of a single standardized cTnT assay, make it a more precise biomarker of AMI [ 6 ]. The cTnT electro-chemiluminescent immunoassay developed by Roche Diagnostics that holds the patent and antibodies underwent many modifications through five generations that ended with Roche becoming the first in vitro diagnostics company to receive the United States Food and Drug administration clearance for a truly high sensitive (hs)-cTnT assay (5th generation) [ 6 , 7 ]. The clinical use of the manufacturer’s declared upper reference limit (URL) for the hs-cTnT assay still does not consider patients’ gender, age or race [ 8 ]. Gender differences in the URL for hs-cTn assays have been reported in a number of small non-specific studies with a trend for higher values in males compared to females especially among young adults [ 9 , 10 ]. The establishment and adoption of a more racial, gender and age-specific URL particularly for hs-cTnT assay would be expected to decrease both over-diagnosis and under diagnosis of AMI [ 8 , 11 ]. particularly in adult males and females respectively. The aim of this work was to establish and compare gender-specific URL for cTnT among adult Egyptians. Subjects and methods Subjects The current study was based on collecting samples from 240 apparently healthy adult Egyptian volunteers aged 18–45 years, divided into 120 males and 120 females, where sample size was adopted according to the approved guidelines for defining, establishing, and verifying reference intervals in the clinical laboratory [document E28–A3, published in 2008 by Clinical Laboratory Standard Institute (CLSI) and International Federation of Clinical Chemistry (IFCC)] [12,13]. A written consent was obtained from every participant included in this study that was approved by the Ethics Committee of Medical Research Institute. The participants were recruited from Mustafa Kamel Military Hospital during their general heath check-up as a prerequisite for applying to various governmental jobs in the period from May to October 2019. Population selection Population selection was based on the most stringent criteria for selection of reference group (normals) as published in 2012 by Collinson et al, as those individuals who gave no history of cardiovascular / vascular disease, hypertension, diabetes mellitus, or heavy alcohol intake and whom had blood pressure ≤140/90 mmHg, fasting serum glucose up to 100 mg/dL, estimated glomerular filtration rate (eGFR) more than 60 mL/min /1.73 m 2 , receiving no cardiac medication and their echocardiography showing left ventricular ejection fraction (LVEF) exceeding 55 % with no significant left ventricular hypertrophy, diastolic heart failure, valvular heart disease or regional wall-motion abnormalities [6]. Furthermore, subjects with normal lung function and no liver affection (free of viral hepatitis B and C affection and with activities of aminotransferases within permissible reference limits for both genders) as well as absent history of pulmonary embolism, sepsis, rhabdomyolysis, burns, drug toxicity, stroke and recent hospitalization within the last six months prior to recruitment in this study were included [14]. Clinical examination To all participants, detailed history taking and thorough physical examination were done, along with echocardiography using the General Electric (GE)-Vivid T8 cardiovascular ultrasound machineto measure left ventricular ejection fraction, to exclude all subclinical cases of cardiovascular disease. Laboratory investigations Laboratory investigations were done on a fasting serum sample obtained from every participant following an overnight (8–10 hours) fasting period with venous blood collected aseptically according to the standardized protocol of sampling developed by the CLSI for cTnT. Portion of the serum was used for the determination of serum levels of glucose and creatinine as well as activities of alanine and aspartate aminotransferases using the cobas c501 module (clinical chemistry unit) of the Cobas 6000 modular analytical system platform utilizing calibrators, control materials and reagents from the manufacturer (Roche Diagnostics, GmbH, D-68305 Mannheim, Germany). Estimated glomerular filtration rate (eGFR) was calculated using the corrected modification of diet in renal disease (MDRD) equation. [15] The rest of the serum sample was used in the determination of cTnT using the 5 th generation hs-cTnT electro-chemiluminescent (ECL) immunoassay on the cobas e601 module (immunoassay unit) of the Cobas 6000 modular analytical system platform (Roche Diagnostics, GmbH, D-68305 Mannheim, Germany). According to the manufacturer of the hs-cTnT ECL assay, no interferences from lipemia (intralipid less than 1500 mg/dl), icterus (bilirubin less than 25 mg/dl), hemolysis (hemoglobin less than 0.1 gm/dl), rheumatoid factor up to a concentration of 1500 IU/mL and biotin less than 20 ng/mL were observed with cTnT. Moreover, the manufacturer declared an assay high-dose hook effect for cTnT concentrations up to 100000 ng/L. According to the manufacturer claims, the assay had a dynamic range of 3.0–10000 ng/L, where 3.0 ng/L corresponded to limit of blank (LOB), whereas limit of detection (LOD) was 5.0 ng/L. The reported limit of quantitation (LOQ) was 13.0 ng/L (guaranteed percent coefficient of variation (%CV) of <10%). In order to verify such claims concerning the precision at 13.0 ng/L (LOQ), a precision verification protocol was applied according to the CLSI approved guidelines (document EP15-A2) (Chesher, 2008) describing protocols undertaken by the user to verify manufacturer’s precision claims. A pooled sample was used in the determination of cTnT with a calculated overall concentration of 13.0 ng/L. The concentration of the pooled sample was then verified by measuring cTnT in triplicate, giving a mean of 12.9 ng/L. The pooled sample was then divided into 5 aliquots containing 200 µl each, where all aliquots were frozen. Each aliquot was determined for cTn as three replicates daily over five days (× 5 days design). Next, a precision validation protocol was also carried out according to the CLSI approved guidelines (document EP15-A2) (Chesher, 2008) to validate the total imprecision of the assay at the proposed 99 th percentile of 10ng/L, a level below the claimed LOQ (13.0 ng/L), by obtaining 10 of the measured serum samples (all measuring around 10.0 ng/L) that were pooled, mixed and homogenized to give a calculated overall concentration of 10.0 ng/L. The concentration of the pooled sample was then verified by measuring it in triplicate, giving a mean of 9.95 ng/L. The pooled sample was then divided into 20 aliquots containing 150 µl each, where all aliquots were frozen. Each aliquot was determined for cTnT twice daily (separated by a minimum of two hours) over the 20 days period (× 20 days design). Statistical analysis It was done using SPSS program version 22 (Statistical Package of social sciences, Released 2013. IBM SPSS Statistics for Windows, Version 22.0. Armonk, NY: IBM Corp) [16] and MedCalc for Windows, version 15.0 (MedCalc Software, Ostend, Belgium) [17].Data were entered as numerical or categorical, as appropriate. Shapiro test for normality was used to test for the significant deviation from normal distribution across all quantitative variables in all (sub) groups. For parametric variables, mean and standard deviation were used, while for non-parametric variables, median and interquartile range (IQR) were used. Mann Whiteny test was used to compare non-parametric variables across groups. The 99th percentile (upper reference limit URL) of serum cTnT was calculated as the absolute single upper 99th percentile value (1–sided 99% reference interval) using the non-parametrical percentile method for the 99 th percentile according to the approved guidelines for defining, establishing, and verifying reference intervals in the clinical laboratory document E28–A3, published in 2008 by Clinical Laboratory Standard Institute (CLSI) and International Federation of Clinical Chemistry (IFCC). [12] Bootstrapping re-sampling procedure was then used to calculate 95% Confidence interval of our calculated 99 th percentile value. Testing for presence of outliers was done using the method described by Reed et al. (1971) [18]. Results Although all participants had an age range from 18–45 years, yet male participants had significantly higher median age value than females. As regards blood pressure measurements, despite the statistically significant difference noted in systolic, diastolic and mean arterial blood pressure median values, yet all did not exceed the 140/90, which is the cut off value for defining hypertension. The left ventricular ejection fraction value was significantly higher in males compared to females, yet all had an ejection fraction above 55% which is considered normal according to the guidelines issued by several cardiology societies Table (1): Age, arterial blood pressure (ABP), and left ventricular ejection fraction among the studied groups Variable All (n=240) Males (n=120) Females (n=120) pMC Age (years) -Mean (95% CI) ± SD. 34.48 (33.49 – 35.47) ± 7.78 35.61 (34.3 – 36.92) ± 7.23 33.35 (31.87 – 34.83) ± 8.17 U= 6036 Z= -2.17 p= 0.029* -Median (IQR) 36 (11) 38 (10.75) 34 (12) -Min. – Max. 18 – 45 18 – 45 18 – 45 Systolic BP (mmHg) -Mean (95% CI) ± SD. 118.29 (117.41 – 119.17) ± 6.94 120.38 (119.2 – 121.55) ± 6.52 116.21 (114.99 – 117.43) ± 6.74 U= 4907 Z= -4.64 p<0.001* -Median (IQR) 120 (10) 120 (10) 120 (10) -Min. – Max. 100 – 135 100 – 135 100 – 130 Diastolic BP (mmHg) -Mean (95% CI) ± SD. 76.21 (75.47 – 76.94) ± 5.79 77.33 (76.33 – 78.33) ± 5.54 75.08 (74.03 – 76.14) ± 5.83 U= 5676 Z= -3.01 p= 0.003* -Median (IQR) 80 (10) 80 (10) 75 (10) -Min. – Max. 60 – 90 60 – 90 60 – 85 Mean Arterial BP (mmHg) -Mean (95% CI) ± SD. 90.23 (89.53 – 90.94) ± 5.55 91.68 (90.74 – 92.61) ± 5.18 88.78 (87.78 – 89.79) ± 5.54 U= 5066 Z= -4.04 p<0.001* -Median (IQR) 91.7 (6.6) 93.3 (8.3) 86.7 (10) -Min. – Max. 73.3 – 103.3 76.7 – 103.3 73.3 – 100 LV ejection fraction (%) -Mean (95% CI) ± SD. 68.55 (68.07 – 69.03) ± 3.76 69.38 (68.67 – 70.08) ± 3.89 67.73 (67.1 – 68.35) ± 3.46 U= 5389 Z= -3.38 p= 0.001* -Median (IQR) 69 (5) 70 (5) 68 (4.75) -Min. – Max. 59 – 77 59 – 77 59 – 74 *: statistically significant; BP: Blood pressure; CI: Confidence interval; IQR: Inter-quartile range; LV: Left ventricular; Min: Minimum; Max: Maximum; p MC: Monte Carlo p-value; SD: Standard deviation; U, Z: Mann Whitney test statistics; significance level at p<0.05 Apart from the eGFR using the MDRD formula which did not show any gender related statistically significant difference, all other selected biochemical parameters determined to all participants, namely serum levels of glucose and creatinine as well as activities of alanine and aspartate aminotransferases, were significantly higher in males compared to females, yet all were within the safely reported reference intervals for the chosen analytes Table (2): Selected biochemical parameters and estimated GFR among the studied groups Variable All (n=240) Males (n=120) Females (n=120) pMC Serum glucose (mg/dL) -Mean (95% CI) ± SD. 89.49 (88.38 – 90.6) ± 8.74 91.43 (89.83 – 93.04) ± 8.86 87.55 (86.07 – 89.03) ± 8.2 U= 5347 Z= -3.45 p= 0.001* -Median (IQR) 89 (16) 91 (14.75) 87.5 (13) -Min. – Max. 70 – 106 70 – 106 71 – 106 Serum creatinine (mg/dL) -Mean (95% CI) ± SD. 0.84 (0.81 – 0.86) ± 0.18 0.94 (0.91 – 0.97) ± 0.16 0.74 (0.71 – 0.76) ± 0.13 U= 2632 Z= -8.61 p<0.001* -Median (IQR) 0.8 (0.3) 0.9 (0.3) 0.7 (0.2) -Min. – Max. 0.5 – 1.2 0.5 – 1.2 0.5 – 1.0 Estimated-GFR (mL/min) -Mean (95% CI) ± SD. 102.24 (98.9 – 105.57) ± 26.22 102.4 (97.62 – 107.18) ± 26.43 102.07 (97.35 – 106.79) ± 26.11 U= 7193 Z= -0.01 p= 0.99 -Median (IQR) 99.65 (32.6) 98.85 (30.9) 101.8 (36.2) -Min. – Max. 63.7 – 230.2 69.6 – 230.2 63.7 – 170.8 Serum ALT (U/L) -Mean (95% CI) ± SD. 23.67 (22.01 – 25.32) ± 13.01 27.64 (24.85 – 30.43) ± 15.43 19.69 (18.18 – 21.21) ± 8.38 U= 5183 Z= -3.75 p<0.001* -Median (IQR) 21 (14.75) 22.5 (19.75) 19.5 (11) -Min. – Max. 6 – 74 7 – 74 6 – 48 Serum AST (U/L) -Mean (95% CI) ± SD. 20.03 (19.08 – 20.97) ± 7.42 22.81 (21.4 – 24.21) ± 7.78 17.24 (16.18 – 18.3) ± 5.88 U= 4140 Z= -5.7 p <0.001* -Median (IQR) 19.5 (9.75) 22 (11.5) 17 (8.75) -Min. – Max. 7 – 40 7 – 40 7 – 34 *: statistically significant; ALT: Alanine aminotransferase; AST: Aspartate aminotransferase; GFR: Glomerular filtration rate; CI: Confidence interval; IQR: Inter-quartile range; LV: Left ventricular; Min: Minimum; Max: Maximum; p MC: Monte Carlo p-value; SD: Standard deviation; U, Z: Mann Whitney test statistics; significance level at p<0.05 As regards serum cTnT value among all the 240 individuals, 86 participants (35.8%) had serum cTnT below Level of detection (LOD). When divided according to gender; 27 (22.5%) out of the 120 male participants had serum cTnT below LOD and 59 (49.2%) out of the 120 females participants had serum cTnT below LOD (all were given a 3.0 ng/L value for sake of proper ranking of all distribution independent non-parametric ranking analyses that follows). Comparing serum cTnT among the two genders revealed a significantly higher level among male subjects (median = 5.5 ng/L) compared to female subjects (median = 3.05 ng/L), (Z=-4.324, p<0.001). The 99 th percentile URL of serum cTnT was first calculated among all of the 240 participants revealing an URL of 15.49 ng/L (95% CI: 11.1-20.1 ng/L) The URL of serum cTnT was then calculated for each gender (120 males and 120 female) independently. No outliers were found among each gender according to outlier detection method developed by Reed et al. (1971). Results showed an URL of 19.55 ng/L (95% CI: 10.89–20.1 ng/L) among male participants and an URL of 12.58 ng/L (95% CI: 9.9–12.6 ng/L) When stratified according to an age cutoff value of 36 years, one group included 119 subjects aged less than 36 years and another group included 121 subjects aged 36 years or more. In the first group 70 out of 119 (58.8%) subjects had a serum cTnT below LOD while in the second group 16 out of 121 (13.2%) subjects had a serum cTnT below LOD (all were given a 3.0 ng/L value for sake of proper ranking of all distribution independent non-parametric ranking analyses that follows). Comparing serum cTnT among the two groups revealed a significantly higher serum cTnT level (median= 6.0 ng/L) among the group aged 36 years old or more compared to its level in the group aged less than 36 years (median= 3.0 ng/L), (U= 3027, Z=-7.96, P<0.001). Based on Reed et al. (1971) outlier detection method, one outlier result was found among the serum cTnT measurements of the group aged less than 36 years (20.1 ng/L) and another outlier in the group aged 36 years old or more (17.5 ng/L). Accordingly, the 99 th percentile URL of serum cTnT was calculated for each age group independently with and without excluding detected outliers. When including outliers (according to CLSI guideline that recommends a conservative policy of not deleting any values), the URL of cTnT was 18.1 ng/L (95% CI: 7.9–20.1 ng/L) for the group less than 36 years old and an URL of 16.42 ng/L (95% CI: 12.08–17.5 ng/L) for the group aged 36 years old or more. When excluding the detected outliers from both groups, the cTnT serum level revealed an URL of 10.0 ng/L (95% CI: 7.6–10.1ng/L) for those aged less than 36 years old and an URL of 12.6 ng/L (95% CI: 11.3–12.6 ng/L) for those aged 36 years or more Still after excluding the detected outliers, serum cTnT was significantly higher in those aged 36 years or more (median= 6.0 ng/L) compared to its level in those aged less than 36 years (median= 3.0 ng/L), (U= 2905.5, Z=-8.068, p<0.001). When comparing serum cTnT level according to gender in both groups of participants divided according to an age value of 36 years old, significantly higher levels were found among males (median= 4.35 ng/L) compared to females (median= 3.0 ng/L) (U= 1161, Z= -3.315, p= 0.001) in the group aged less than 36 years old, which was not the case for those aged 36 years old or more, as no statistically significant difference was noted in its levels between males (median= 6.35 ng/L) and females (median= 5.2 ng/L) (U=413.5, Z=-1.854, p=0.061). In order to verify the degree of imprecision of the hs-cTnT assay claimed by the manufacturer, the daily triplicate × 5 days design recommended by CLSI for verification of the manufacturer claimed precision for a pooled specimen with a calculated mean value of 13.0 ng/L showed an overall mean value of 12.9 ng/L and a SD of 0.864 ng/L with a percent coefficient of variation (%CV) of 6.7%, a minimum value of 11.8 ng/L and a maximum value of 14.0 ng/L, with no outliers detected. In order to validate the assay’s degree of imprecision at 10.0 ng/L (our lowest 99 th percentile which is below the assay’s claimed LOQ of 13.0 ng/L), the daily duplicate × 20 days design recommended by CLSI for precision validation was used and revealed for a pooled serum sample with a calculated mean value of 10.0 ng/L an overall measured mean value of 9.95 ng/L, a standard deviation of 0.761 ng/L, and a %CV of 7.7%, with a minimum value of 8.99 ng/L and a maximum value of 11.0 ng/L, with no outliers detected. Looking closely into the manufacturer precision assessment section of our kit, the tables showed that regarding the Cobas e411 analyzer %CV equal to 15% and 5.2% were calculated for intermediate precision at mean value of 7.5 ng/L and 13.5 ng/L, yet regarding the Cobas e601 module (immunoassay unit) of the Cobas 6000 modular analytical system (used in the current study), %CV equal to 8.6 and 5.2 were calculated for intermediate precision at mean values of 6.5 ng/L and 11 ng/L. Thus, the manufacturer adopted the higher CV% of less precise Cobas e411 to be the overall CV% used to determine its LOQ of the kit , calming the limit of quantitation (LOQ) at 13.0 ng/L guarantee a (%CV) of <10% on all its platform when in reality as proved by the manufacturer own study and confirm by our precision study, the cobas e601 module is in fact more precis than e411 and a lower LOQ of 10 ng/L or even lower can be adopted and still guarantee a (%CV) of <10% as recommended. Discussion The rise of IHD, particularly acute myocardial infarction (AMI), among young and middle aged adults (18–45 years) and its effect on personal and economic productivity, has driven worldwide efforts for decreasing its burden [ 19 ]. Premature AMI refers to MI in men 55 years or less and in women 65 years or less. There are limited international studies on the relationship between risk factors (demographics, lifestyle factors, clinical risk factors and biomarkers) and premature MI. A study showed that these risk factors were higher among young versus elderly people [ 20 ]. Furthermore, women remain the majority who die from cardiovascular disease (CVD), with an estimated 515,000 women each year diagnosed with coronary heart disease. Data indicate that CVD mortality among young women between the ages of 35 and 54 years is increasing due to some risk factors that are exclusive to women such as pregnancy-related complications, polycystic ovaries and oral contraceptives pills as well as other risk factors that are more prevalent in women than men such as mental stress induced ischemia, depression, and anxiety [ 21 ]. According to the new universal definition, the only recommended diagnostic biomarkers for evaluation of myocardial injury and AMI are cardiac troponins (cTn) [ 3 ], where cTnT immunoassay shows far better performance compared to cTnI immunoassays. The problem with the currently available cTn assays is their inability to discriminate between males and females, particularly among young and middle aged adults, concerning the 99th percentile URL that can safely discriminate an acute infarct from a non-infarct. The establishment and adoption of a more racial, gender and age-specific URL for cTn assays, particularly the more specific hs-cTnT assay, would be expected to decrease both over-diagnosis and under diagnosis of AMI, particularly in young and middle aged adults. The current study was done to establish a valid 99th percentile URL for serum cTnT among adult male and female subjects. There is much debate concerning both, the selection of a healthy reference population in determining cTns 99th percentile values. However, recent studies have shown that the selection criteria applied to define a healthy reference population may greatly influence the derived 99th percentile values for cTns. [ 22 ]. Unfortunately to date, no evidence based guidelines or universal protocols have been formally implemented to support laboratories and manufacturers in establishing 99th percentile URLs for cTns [ 23 ]. In multiple studies, several approaches have been proposed, ranging from data collection from self-reported questionnaires to screening with laboratory surrogate biomarkers, cardiac imaging techniques and other diagnostic tests, in order to evaluate the health status of individuals constituting a normal reference population [ 24 ]. A study done by Sandoval and Apple suggested that the screening and enrolment of presumably healthy individuals into a study to determine the 99th percentile URL for cTn assay should minimally address the following; clinical history for known cardiovascular disease and medication usage, surrogate biomarkers for diabetes and renal dysfunction, appropriate non-parametric statistical analysis, possible inclusion of an imaging modality if financially feasible and a description of specimen type used [ 7 ]. The study was based on collecting serum samples from 240 apparently healthy young adult Egyptian volunteers aged 18–45 years, divided into 120 males and 120 females for measuring serum cTnT using the 5th generation hs-cTnT assay. The current study identified that gender was an important factor influencing its serum concentrations. Comparing serum cTnT among the two genders revealed a significantly higher level among male compared to female subjects (Z= -4.324, p < 0.001). Consequently, the derived 99th percentile value for cTnT in this study in female participants was lower (12.58 g/L) than that of male participants (19.55 ng/L). This observation was in agreement with Collinson et al whom reported a clear difference between men and women in the examined subgroups for the Roche hs-cTnT ECL immunoassay.[ 25 ] Several other studies support the existence of a discrepancy between percentile values of cTnT in men and women [ 26 , 27 , 28 , 29 , 30 , 31 ]. Studies concerning gender-specific lower thresholds for women for the diagnosis of AMI have not shown consistent results. Shah et al. (2015) proposed that women-specific lower diagnostic thresholds for cTn may double the diagnosis of AMI in women, and identify those at high risk of re-infarction and death [ 32 ]. On the other hand, a study by Giménez et al. (2016) done on a larger sample size, demonstrated that gender-specific troponin thresholds did not improve diagnostic accuracy, and hence has proposed that the 99th percentile should remain the standard of care for both genders [ 33 ]. The potentially profound clinical importance of gender specific cutoff values would be evident when the use of gender specific diagnostic thresholds for cTns markedly increase the diagnosis of MI in women and improve the outcomes. In our study, the effect of age was obvious on serum cTnT levels when participants were divided according to an age cutoff value of 36 years, where serum cTnT levels were significantly lower in 119 subjects aged < 36 years old compared to 121 subjects aged 36 years old or more (p < 0.001), with a proposed 99th percentile cutoff value of 18.1 ng/L and 16.42 ng/L respectively after including outliers according to the CLSI recommendations, and 10.0 ng/L and 12.6 ng/L respectively with excluding of outliers. Moreover, a serum cTnT level comparison across gender was done in both age groups revealing a significantly higher value of serum cTnT among males compared to females in those aged less than 36 years old (p = 0.001). Such a gender related significant difference was lost in those aged 36 years old or more (p = 0.061). In conclusion, a constant URL of 14.0 ng/L for the hs-cTnT assay in the diagnosis of AMI as proposed by the manufacturer in a study involving 533 healthy volunteers (age range: 20–71 years) (95% confidence interval = 12.7–24.9 ng/L) does not reflect the 99th percentile value of a reference population with varied demographic characteristics. Instead, we propose that use of age and gender specific 99th percentile value as an URL for hs-cTnT assay would benefit the patient in early diagnosis of AMI and decrease false positive AMI diagnosis with the hs-cTnT assay, a problem with major clinical and public health ramifications. Further studies are needed to verify whether such age and gender specific cutoff values could improve the diagnostic performance of cTnT for AMI. Abbreviations CK-MB Muscle brain fraction of creatine kinase CLSI Clinical Laboratory Standard Institute FAG Antigen –binding fragment cTn Cardiac troponins C-TnC C-terminal domains of TnC hs-cTnT High sensitive-Cardiac troponin-T Declarations Ethics declarations Conflicts of interest None to declare by the authors of this manuscript Ethical approval and consent to participate This study was performed at the Medical Research Institute hospital. approval was granted by the Ethics committee of the Medical Research Institute, Alexandria University (approval number: E/C.S/N.T84/2019). All volunteers gave informed and written consent. Competing interests The authors have no relevant financial or non-financial interests to disclose. Author Contribution A.T. and A.R. contributed to the conception , design of the work; the acquisition ,analysis, and interpretation; M. L. supervised the case selection and conducted the clinical part; A.A and A.T wrote and revised the manuscript; All authors have reviewed and approved the final version of the manuscript. References Chandrasekhar, J., Gill, A., & Mehran, R. (2018). Acute myocardial infarction in young women: current perspectives. International journal of women's health, 10, 267-284. Morrow, D. A., Cannon, C. P., Jesse, R. L., Newby, L. K., Ravkilde, J., Storrow, A. B. . . . & Christenson, R. H. (2007). National Academy of Clinical Biochemistry Laboratory Medicine Practice Guidelines: Clinical characteristics and utilization of biochemical markers in acute coronary syndromes. Circulation, 115(13), e356-375. Thygesen, K., Alpert, J. S., Jaffe, A. S., Chaitman, B. R., Bax, J. J., Morrow, D. A., & White, H. D. (2018). Fourth Universal Definition of Myocardial Infarction (2018). Journal of the American College of Cardiology, 25285. Giannitsis, E., Kurz, K., Hallermayer, K., Jarausch, J., Jaffe, A. S., & Katus, H. A. (2010). Analytical validation of a high-sensitivity cardiac troponin T assay. Clinical chemistry, 56(2), 254-261. Herman, D. S., Kavsak, P. A., & Greene, D. N. (2017). Variability and Error in Cardiac Troponin Testing: An ACLPS Critical Review. American journal of clinical pathology, 148(4), 281-295. Apple, F. S., & Collinson, P. O. (2012). Analytical characteristics of high-sensitivity cardiac troponin assays. Clinical chemistry, 58(1), 54-61. Apple, F. S., Sandoval, Y., Jaffe, A. S., & Ordonez-Llanos, J. (2017). Cardiac Troponin Assays: Guide to Understanding Analytical Characteristics and Their Impact on Clinical Care. Clinical chemistry, 63(1), 73. de Lemos, J. A. (2013). Increasingly sensitive assays for cardiac troponins: a review. Journal of the American medical association, 309(21), 2262-2269. Kimenai, D. M., Janssen, E., Eggers, K. M., Lindahl, B., den Ruijter, H. M., Bekers, O. . . . & Meex, S. J. R. (2018). Sex-Specific Versus Overall Clinical Decision Limits for Cardiac Troponin I and T for the Diagnosis of Acute Myocardial Infarction: A Systematic Review. Clinical chemistry, 64(7), 1034-1043. Shah, A. S. V., Ferry, A. V., & Mills, N. L. (2017). Cardiac Biomarkers and the Diagnosis of Myocardial Infarction in Women. Current cardiology reports, 19(5), 40-40. Romiti, G. F., Cangemi, R., Toriello, F., Ruscio, E., Sciomer, S., Moscucci, F. . . . & Raparelli, V. (2019). Sex-Specific Cut-Offs for High-Sensitivity Cardiac Troponin: Is Less More? Cardiovascular therapeutics, 2019, 9546931-9546931. Horowitz, G. L. (2008). Reference Intervals: Practical Aspects. Electronic journal of the international federation of clinical chemistry, 19(2), 95-105. Horowitz, G. L., Altaie, S., Boyd, J. C., Ceriotti, F., Garg, U., Horn, P. . . . & Zakowski, J. (2008). Defining, establishing, and verifying reference intervals in the clinical laboratory; approved guideline vol. 28. 3 rd ed. CLSI document E28–A3. Wayne, PA: Clinical and Laboratory Standards Institute. Tanindi, A., & Cemri, M. (2011). Troponin elevation in conditions other than acute coronary syndromes. Vascular health and risk management, 7, 597-603. McKie, P. M., Heublein, D. M., Scott, C. G., Gantzer, M. L., Mehta, R. A., Rodeheffer, R. J. . . . & Jaffe, A. S. (2013). Defining High-Sensitivity Cardiac Troponin Concentrations in the Community. Clinical chemistry, 59(7), 1099. Puri, B. (2002). SPSS in Practice 2 nd ed. An illustrated guide: Taylor & Francis. Daly, L., & Bourke, G. J. (2008). Interpretation and Uses of Medical Statistics. United States: Wiley. Reed, A. H., Henry, R. J., & Mason, W. B. (1971). Influence of statistical method used on the resulting estimate of normal range. Clinical chemistry, 17(4), 275-284. Benjamin, E. J., Blaha, M. J., Chiuve, S. E., Cushman, M., Das, S. R., Deo, R. . . . & Stroke Statistics, S. (2017). Heart Disease and Stroke Statistics-2017 Update: A Report From the American Heart Association. Circulation, 135(10), e146-e603. Dugani, S. B., Ayala Melendez, A. P., Reka, R., Hydoub, Y. M., McCafferty, S. N., Murad, M. H. . . . & Mora, S. (2019). Risk factors associated with premature myocardial infarction: a systematic review protocol. British medical journal open, 9(2), e023647-e023647. Mehta, P. K., Wei, J., & Wenger, N. K. (2015). Ischemic heart disease in women: a focus on risk factors. Trends in cardiovascular medicine, 25(2), 140-151. Aw, T. C., Huang, W. T., Le, T. T., Pua, C. J., Ang, B., Phua, S. K. . . . & Chin, C. (2018). High-Sensitivitycardiac Troponinsin Cardio-Healthy Subjects: A Cardiovascular Magnetic Resonance Imaging Study. Scientific reports, 8(1), 15409-15409. Kozinski, M., Krintus, M., Kubica, J., & Sypniewska, G. (2017). High-sensitivity cardiac troponin assays: From improved analytical performance to enhanced risk stratification. Critical Reviews in Clinical Laboratory Sciences, 54(3), 143-172. Krintus, M., Kozinski, M., Boudry, P., Lackner, K., Lefevre, G., Lennartz, L. . . . & Sypniewska, G. (2015). Defining normality in a European multinational cohort: Critical factors influencing the 99th percentile upper reference limit for high sensitivity cardiac troponin I. International journal of cardiology, 187, 256-263. Collinson, P. O., Heung, Y. M., Gaze, D., Boa, F., Senior, R., Christenson, R., & Apple, F. S. (2020). Influence of Population Selection on the 99th Percentile Reference Value for Cardiac Troponin Assays. Clinical chemistry, 58(1), 219-225. Kimenai, D. M., Henry, R. M., van der Kallen, C. J., Dagnelie, P. C., Schram, M. T., Stehouwer, C. D. . . . & Meex, S. J. (2016). Direct comparison of clinical decision limits for cardiac troponin T and I. Heart, 102(8), 610-616. Mueller, T., Egger, M., Leitner, I., Gabriel, C., Haltmayer, M., & Dieplinger, B. (2016). Reference values of galectin-3 and cardiac troponins derived from a single cohort of healthy blood donors. Clinica chimica act, 456, 19-23. Yang, S., Huai, W., Qiao, R., Cui, L., Liu, G., Wu, J. . . . & Zhang, J. (2016). Age and Gender Tailored Cut-off Value of hs-cTnT Contributes to Rapidly Diagnose Acute Myocardial Infarction in Chest Pain Patients. Clinical laboratory, 62(8), 1451-1459. Monneret, D., Gellerstedt, M., & Bonnefont-Rousselot, D. (2018). Determination of age- and sex-specific 99th percentiles for high-sensitive troponin T from patients: an analytical imprecision- and partitioning-based approach. Clinical chemistry and laboratory medicine, 56(5), 685-696. Ungerer, J. P. J., Tate, J. R., & Pretorius, C. J. (2020). Discordance with 3 Cardiac Troponin I and T Assays: Implications for the 99th Percentile Cut-off. Clinical chemistry, 62(8), 1106-1114. Welsh, P., Preiss, D., Shah, A. S. V., McAllister, D., Briggs, A., Boachie, C. . . . & Sattar, N. (2020). Comparison between High-Sensitivity Cardiac Troponin T and Cardiac Troponin I in a Large General Population Cohort. Clinical chemistry, 64(11), 1607-1616. Shah, A. S. V., Griffiths, M., Lee, K. K., McAllister, D. A., Hunter, A. L., Ferry, A. V. . . . & Mills, N. L. (2015). High sensitivity cardiac troponin and the under-diagnosis of myocardial infarction in women: prospective cohort study. British medical journal, 350, g7873. Rubini Gimenez, M., Twerenbold, R., Boeddinghaus, J., Nestelberger, T., Puelacher, C., Hillinger, P. . . . & Mueller, C. (2016). Clinical Effect of Sex-Specific Cut-off Values of High-Sensitivity Cardiac Troponin T in Suspected Myocardial Infarction. Journal of the American Medical Association cardiology, 1(8), 912-920. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-5299564","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":369426520,"identity":"892e3aad-5493-4c2f-9e52-ecfca1653231","order_by":0,"name":"Ahmed Tork","email":"","orcid":"","institution":"Alexandria University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Ahmed","middleName":"","lastName":"Tork","suffix":""},{"id":369426521,"identity":"29dde0f2-c8ef-4a9b-87ef-590119b1970d","order_by":1,"name":"Mohamed Labib","email":"","orcid":"","institution":"Alexandria University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Mohamed","middleName":"","lastName":"Labib","suffix":""},{"id":369426522,"identity":"62fa732d-5d9e-4b15-8736-b597644435c0","order_by":2,"name":"Abeer Rabea","email":"","orcid":"","institution":"Alexandria University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Abeer","middleName":"","lastName":"Rabea","suffix":""},{"id":369426523,"identity":"b080a3bd-83b7-4cc4-8c64-f42aaa0c511d","order_by":3,"name":"Abeer Ali","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA/UlEQVRIiWNgGAWjYDACCQglw8bewHgAwk4gTgsPG88BBhK1MEgkEKmFf3bzwccVDHY8fJKPHxz42HaYgZ89x4Dhwy88ltw5lmx4hiGZh006zeDgjDOHGSR73hgwzuzDY82NHDPJBgZmoJYEg8M8FYcZDG7kGDDz9uDWIX8j//vPBoZ6HjbJ4x8O/zE4zGAP0vIXjxagmWyMDQyHedgkeIDqQbZIALUw/MCtxfDOMWPJBoPjwEDOKTjYcyadR+LMs4KDvQ24tcjdbn74saGiWk6+/fjGBz/brOX425M3PvjxB4/3Ic5DMHlAxAHGNkJaMAFBW0bBKBgFo2AEAQC07FD16gmQWwAAAABJRU5ErkJggg==","orcid":"","institution":"Alexandria University","correspondingAuthor":true,"submittingAuthor":false,"prefix":"","firstName":"Abeer","middleName":"","lastName":"Ali","suffix":""}],"badges":[],"createdAt":"2024-10-20 17:53:06","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5299564/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5299564/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":67442380,"identity":"f5261821-01e1-46fc-9a99-5f9c36da491f","added_by":"auto","created_at":"2024-10-25 06:09:19","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":235719,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFig. 1.1: \u0026nbsp;(A/B/C):\u003c/strong\u003e Upper reference limit for serum cTnT among all subjects, and when divided according to gender\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFig. 1.1: (D):\u003c/strong\u003e Upper reference limit for serum cTnT among among female participants.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-5299564/v1/2e173f45fa8f5ed512905f78.png"},{"id":67442378,"identity":"79bf8825-1ef5-4978-9c88-0fda3f1e346d","added_by":"auto","created_at":"2024-10-25 06:09:18","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":370716,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFig. 1.2.a: (A/B/C): \u003c/strong\u003eUpper reference limit for cTnT according to an age cut-off value of 36 years, including outliers in both groups\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFig. 1.2.b: \u0026nbsp;(A/B/C): \u003c/strong\u003eUpper reference limit for serum cTnT according to an age cut-off value of 36 years, excluding outliers in both groups\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-5299564/v1/9b6f66a0d5da7732416f4d25.png"},{"id":77396842,"identity":"4885eab7-f090-49aa-a4c2-45119f688e26","added_by":"auto","created_at":"2025-02-28 07:47:09","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1319350,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5299564/v1/aa7d7737-cc53-4f35-a147-9ea11f536528.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Establishment of gender related 99th percentile values for cardiac troponin-T among young and middle-aged adult Egyptians ","fulltext":[{"header":"Introduction","content":"\u003cp\u003eCoronary artery disease accounts for 15.9% of all deaths worldwide. Acute myocardial infarction (AMI) is still the first cause of death among women all over the world, where more than 30,000 young women\u0026thinsp;\u0026lt;\u0026thinsp;55 years of age are hospitalized with AMI every year in the United States alone. The rising incidence of AMI among younger women in recent decades goes hand in hand with the rising incidence of diabetes mellitus, metabolic syndrome, polycystic ovaries and non-traditional risk factors such as anxiety, depression, stress and the use of oral contraceptives pills [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eCirculating levels of cardiac troponins (cTn) are nowadays considered the preferred biomarkers in the diagnosis of acute myocardial infarction (AMI). In peripheral blood, after onset of myocardial injury cardiac troponins begin to rise within 3 to 4 hours and remain elevated for 10 to 14 days [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. According to the Fourth Universal Definition of Myocardial Infarction published in August 2018; detection of an elevated cTn value above the 99th percentile upper reference limit (URL) is defined as myocardial injury, where injury is considered acute if there is a rise and/or fall of cTn values [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eTwo types of assays exist for cardiac troponins; cardiac troponin-I (cTnI) and cardiac troponin-T (cTnT) immunoassays. Different available cTnI immunoassays use different capture and detection antibodies that recognize different epitopes of cTnI with different affinities for its various forms in the circulation, whether resulting from post-translational modifications [proteolytic degradation, phosphorylation, oxidation and reduction] or complexing with other molecules [Troponin-C, heparin, heterophile or human antimouse antibodies, and cTnI specific autoantibodies circulating in blood] [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Moreover, the lack of a commutable reference material that standardize cTnI results makes absolute concentrations of cTnI determined by different immunoassays very inconsistent even for different assays and instruments marketed by the same manufacturer [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eOn the other hand, the more stable nature of cTnT molecule in circulation and the worldwide availability of a single standardized cTnT assay, make it a more precise biomarker of AMI [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. The cTnT electro-chemiluminescent immunoassay developed by Roche Diagnostics that holds the patent and antibodies underwent many modifications through five generations that ended with Roche becoming the first in vitro diagnostics company to receive the United States Food and Drug administration clearance for a truly high sensitive (hs)-cTnT assay (5th generation) [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe clinical use of the manufacturer\u0026rsquo;s declared upper reference limit (URL) for the hs-cTnT assay still does not consider patients\u0026rsquo; gender, age or race [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. Gender differences in the URL for hs-cTn assays have been reported in a number of small non-specific studies with a trend for higher values in males compared to females especially among young adults [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. The establishment and adoption of a more racial, gender and age-specific URL particularly for hs-cTnT assay would be expected to decrease both over-diagnosis and under diagnosis of AMI [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. particularly in adult males and females respectively. The aim of this work was to establish and compare gender-specific URL for cTnT among adult Egyptians.\u003c/p\u003e"},{"header":"Subjects and methods","content":"\u003cp\u003e\u003cstrong\u003eSubjects\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe current study was based on collecting samples from 240 apparently healthy adult Egyptian volunteers aged 18\u0026ndash;45 years, divided into 120 males and 120 females, where sample size was adopted according to the approved guidelines for defining, establishing, and verifying reference intervals in the clinical laboratory [document E28\u0026ndash;A3, published in 2008 by Clinical Laboratory Standard Institute (CLSI) and International Federation of Clinical Chemistry (IFCC)] [12,13].\u003c/p\u003e\n\u003cp\u003eA written consent was obtained from every participant included in this study that was approved by the Ethics Committee of Medical Research Institute. The participants were recruited from Mustafa Kamel Military Hospital during their general heath check-up as a prerequisite for applying to various governmental jobs in the period from May to October 2019.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePopulation selection\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003ePopulation selection was based on the most stringent criteria for selection of reference group (normals) as published in 2012 by Collinson et al, as those individuals who gave no history of cardiovascular / vascular disease, hypertension, diabetes mellitus, or heavy alcohol intake and whom had blood pressure \u0026le;140/90 mmHg, fasting serum glucose up to 100 mg/dL, estimated glomerular filtration rate (eGFR) more than 60 mL/min /1.73 m\u003csup\u003e2\u003c/sup\u003e, receiving no cardiac medication and their echocardiography showing left ventricular ejection fraction (LVEF) exceeding 55 % with no significant left ventricular hypertrophy, diastolic heart failure, valvular heart disease or regional wall-motion abnormalities [6]. Furthermore, subjects with normal lung function and no liver affection (free of viral hepatitis B and C affection and with activities of aminotransferases within permissible reference limits for both genders) as well as absent history of pulmonary embolism, sepsis, rhabdomyolysis, burns, drug toxicity, stroke and recent hospitalization within the last six months prior to recruitment in this study were included [14].\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eClinical examination\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eTo all participants, detailed history taking and thorough physical examination were done, along with echocardiography using the General Electric (GE)-Vivid T8 cardiovascular ultrasound machineto measure left ventricular ejection fraction, to exclude all subclinical cases of cardiovascular disease.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eLaboratory investigations\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eLaboratory investigations were done on a fasting serum sample obtained from every participant following an overnight (8\u0026ndash;10 hours) fasting period with venous blood collected aseptically according to the standardized protocol of sampling developed by the CLSI for cTnT. Portion of the serum was used for the determination of serum levels of glucose and creatinine as well as activities of alanine and aspartate aminotransferases using the cobas c501 module (clinical chemistry unit) of the Cobas 6000 modular analytical system platform utilizing calibrators, control materials and reagents from the manufacturer (Roche Diagnostics, GmbH, D-68305 Mannheim, Germany). Estimated glomerular filtration rate (eGFR) was calculated using the corrected modification of diet in renal disease (MDRD) equation. [15] The rest of the serum sample was used in the determination of cTnT using the 5\u003csup\u003eth\u003c/sup\u003e generation hs-cTnT electro-chemiluminescent (ECL) immunoassay on the cobas e601 module (immunoassay unit) of the Cobas 6000 modular analytical system platform (Roche Diagnostics, GmbH, D-68305 Mannheim, Germany).\u003c/p\u003e\n\u003cp\u003eAccording to the manufacturer of the hs-cTnT ECL assay, no interferences from lipemia (intralipid less than 1500 mg/dl), icterus (bilirubin less than 25 mg/dl), hemolysis (hemoglobin less than 0.1 gm/dl), rheumatoid factor up to a concentration of 1500 IU/mL and biotin less than 20 ng/mL were observed with cTnT. Moreover, the manufacturer declared an assay high-dose hook effect for cTnT concentrations up to 100000 ng/L.\u003c/p\u003e\n\u003cp\u003eAccording to the manufacturer claims, the assay had a dynamic range of 3.0\u0026ndash;10000 ng/L, where 3.0 ng/L corresponded to limit of blank (LOB), whereas limit of detection (LOD) was 5.0 ng/L. The reported limit of quantitation (LOQ) was 13.0 ng/L (guaranteed percent coefficient of variation (%CV) of \u0026lt;10%). In order to verify such claims concerning the precision at 13.0 ng/L (LOQ), a precision verification protocol was applied according to the CLSI approved guidelines (document EP15-A2) (Chesher, 2008) describing protocols undertaken by the user to verify manufacturer\u0026rsquo;s precision claims. A pooled sample was used in the determination of cTnT with a calculated overall concentration of 13.0 ng/L. The concentration of the pooled sample was then verified by measuring cTnT in triplicate, giving a mean of 12.9 ng/L. The pooled sample was then divided into 5 aliquots containing 200 \u0026micro;l each, where all aliquots were frozen. Each aliquot was determined for cTn as three replicates daily over five days (\u0026times; 5 days design). Next, a precision validation protocol was also carried out according to the CLSI approved guidelines (document EP15-A2) (Chesher, 2008) to validate the total imprecision of the assay at the proposed 99\u003csup\u003eth\u003c/sup\u003e percentile of 10ng/L, a level below the claimed LOQ (13.0 ng/L), by obtaining 10 of the measured serum samples (all measuring around 10.0 ng/L) that were pooled, mixed and homogenized to give a calculated overall concentration of 10.0 ng/L. The concentration of the pooled sample was then verified by measuring it in triplicate, giving a mean of 9.95 ng/L. The pooled sample was then divided into 20 aliquots containing 150 \u0026micro;l each, where all aliquots were frozen. Each aliquot was determined for cTnT twice daily (separated by a minimum of two hours) over the 20 days period (\u0026times; 20 days design).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eStatistical analysis\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eIt was done using SPSS program version 22 (Statistical Package of social sciences, Released 2013. IBM SPSS Statistics for Windows, Version 22.0. Armonk, NY: IBM Corp) [16] and MedCalc for Windows, version 15.0 (MedCalc Software, Ostend, Belgium) [17].Data were entered as numerical or categorical, as appropriate. Shapiro test for normality was used to test for the significant deviation from normal distribution across all quantitative variables in all (sub) groups. For parametric variables, mean and standard deviation were used, while for non-parametric variables, median and interquartile range (IQR) were used. Mann Whiteny test was used to compare non-parametric variables across groups. The 99th percentile (upper reference limit URL) of serum cTnT was calculated as the absolute single upper 99th percentile value (1\u0026ndash;sided 99% reference interval) using the non-parametrical percentile method for the 99\u003csup\u003eth\u003c/sup\u003e percentile according to the approved guidelines for defining, establishing, and verifying reference intervals in the clinical laboratory document E28\u0026ndash;A3, published in 2008 by Clinical Laboratory Standard Institute (CLSI) and International Federation of Clinical Chemistry (IFCC). [12] Bootstrapping re-sampling procedure was then used to calculate 95% Confidence interval of our calculated 99\u003csup\u003eth\u003c/sup\u003e percentile value. Testing for presence of outliers was done using the method described by Reed et al. (1971) [18].\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003eAlthough all participants had an age range from 18\u0026ndash;45 years, yet male participants had significantly higher median age value than females. As regards blood pressure measurements, despite the statistically significant difference noted in systolic, diastolic and mean arterial blood pressure median values, yet all did not exceed the 140/90, which is the cut off value for defining hypertension. The left ventricular ejection fraction value was significantly higher in males compared to females, yet all had an ejection fraction above 55% which is considered normal according to the guidelines issued by several cardiology societies\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable (1): Age, arterial blood pressure (ABP), and left ventricular ejection fraction among the studied groups\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cdiv align=\"\"\u003e\n \u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"618\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 139px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eVariable\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eAll (n=240)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eMales (n=120)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eFemales (n=120)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 83px;\"\u003e\n \u003cp\u003e\u003cstrong\u003epMC\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"5\" style=\"width: 618px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eAge (years)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 139px;\"\u003e\n \u003cp\u003e-Mean (95% CI) \u0026plusmn; SD.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e34.48\u003c/p\u003e\n \u003cp\u003e(33.49 \u0026ndash; 35.47)\u003c/p\u003e\n \u003cp\u003e\u0026plusmn; 7.78\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e35.61\u003c/p\u003e\n \u003cp\u003e(34.3 \u0026ndash; 36.92)\u003c/p\u003e\n \u003cp\u003e\u0026plusmn; 7.23\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e33.35\u003c/p\u003e\n \u003cp\u003e(31.87 \u0026ndash; 34.83)\u003c/p\u003e\n \u003cp\u003e\u0026plusmn; 8.17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"3\" style=\"width: 83px;\"\u003e\n \u003cp\u003eU= 6036 Z= -2.17 p= 0.029*\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 139px;\"\u003e\n \u003cp\u003e-Median (IQR)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e36 (11)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e38 (10.75)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e34 (12)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 139px;\"\u003e\n \u003cp\u003e-Min. \u0026ndash; Max.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e18 \u0026ndash; 45\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e18 \u0026ndash; 45\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e18 \u0026ndash; 45\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"5\" style=\"width: 618px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eSystolic BP (mmHg)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 139px;\"\u003e\n \u003cp\u003e-Mean (95% CI) \u0026plusmn; SD.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e118.29\u003c/p\u003e\n \u003cp\u003e(117.41 \u0026ndash; 119.17)\u003c/p\u003e\n \u003cp\u003e\u0026plusmn; 6.94\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e120.38\u003c/p\u003e\n \u003cp\u003e(119.2 \u0026ndash; 121.55)\u003c/p\u003e\n \u003cp\u003e\u0026plusmn; 6.52\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e116.21\u003c/p\u003e\n \u003cp\u003e(114.99 \u0026ndash; 117.43)\u003c/p\u003e\n \u003cp\u003e\u0026plusmn; 6.74\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"3\" style=\"width: 83px;\"\u003e\n \u003cp\u003eU= 4907\u003c/p\u003e\n \u003cp\u003eZ= -4.64\u0026nbsp;\u003c/p\u003e\n \u003cp\u003ep\u0026lt;0.001*\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 139px;\"\u003e\n \u003cp\u003e-Median (IQR)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e120 (10)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e120 (10)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e120 (10)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 139px;\"\u003e\n \u003cp\u003e-Min. \u0026ndash; Max.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e100 \u0026ndash; 135\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e100 \u0026ndash; 135\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e100 \u0026ndash; 130\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"5\" style=\"width: 618px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eDiastolic BP (mmHg)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 139px;\"\u003e\n \u003cp\u003e-Mean (95% CI) \u0026plusmn; SD.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e76.21\u003c/p\u003e\n \u003cp\u003e(75.47 \u0026ndash; 76.94)\u003c/p\u003e\n \u003cp\u003e\u0026plusmn; 5.79\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e77.33\u003c/p\u003e\n \u003cp\u003e(76.33 \u0026ndash; 78.33)\u003c/p\u003e\n \u003cp\u003e\u0026plusmn; 5.54\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e75.08\u003c/p\u003e\n \u003cp\u003e(74.03 \u0026ndash; 76.14)\u003c/p\u003e\n \u003cp\u003e\u0026plusmn; 5.83\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"3\" style=\"width: 83px;\"\u003e\n \u003cp\u003eU= 5676 Z= -3.01 p= 0.003*\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 139px;\"\u003e\n \u003cp\u003e-Median (IQR)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e80 (10)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e80 (10)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e75 (10)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 139px;\"\u003e\n \u003cp\u003e-Min. \u0026ndash; Max.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e60 \u0026ndash; 90\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e60 \u0026ndash; 90\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e60 \u0026ndash; 85\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"5\" style=\"width: 618px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eMean Arterial BP (mmHg)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 139px;\"\u003e\n \u003cp\u003e-Mean (95% CI) \u0026plusmn; SD.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e90.23\u003c/p\u003e\n \u003cp\u003e(89.53 \u0026ndash; 90.94)\u003c/p\u003e\n \u003cp\u003e\u0026plusmn; 5.55\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e91.68\u003c/p\u003e\n \u003cp\u003e(90.74 \u0026ndash; 92.61)\u003c/p\u003e\n \u003cp\u003e\u0026plusmn; 5.18\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e88.78\u003c/p\u003e\n \u003cp\u003e(87.78 \u0026ndash; 89.79)\u003c/p\u003e\n \u003cp\u003e\u0026plusmn; 5.54\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"3\" style=\"width: 83px;\"\u003e\n \u003cp\u003eU= 5066 Z= -4.04\u0026nbsp;\u003c/p\u003e\n \u003cp\u003ep\u0026lt;0.001*\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 139px;\"\u003e\n \u003cp\u003e-Median (IQR)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e91.7 (6.6)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e93.3 (8.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e86.7 (10)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 139px;\"\u003e\n \u003cp\u003e-Min. \u0026ndash; Max.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e73.3 \u0026ndash; 103.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e76.7 \u0026ndash; 103.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e73.3 \u0026ndash; 100\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"5\" style=\"width: 618px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eLV ejection fraction (%)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 139px;\"\u003e\n \u003cp\u003e-Mean (95% CI) \u0026plusmn; SD.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e68.55\u003c/p\u003e\n \u003cp\u003e(68.07 \u0026ndash; 69.03)\u003c/p\u003e\n \u003cp\u003e\u0026plusmn; 3.76\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e69.38\u003c/p\u003e\n \u003cp\u003e(68.67 \u0026ndash; 70.08)\u003c/p\u003e\n \u003cp\u003e\u0026plusmn; 3.89\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e67.73\u003c/p\u003e\n \u003cp\u003e(67.1 \u0026ndash; 68.35)\u003c/p\u003e\n \u003cp\u003e\u0026plusmn; 3.46\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"3\" style=\"width: 83px;\"\u003e\n \u003cp\u003eU= 5389\u003c/p\u003e\n \u003cp\u003eZ= -3.38 p= 0.001*\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 139px;\"\u003e\n \u003cp\u003e-Median (IQR)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e69 (5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e70 (5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e68 (4.75)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 139px;\"\u003e\n \u003cp\u003e-Min. \u0026ndash; Max.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e59 \u0026ndash; 77\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e59 \u0026ndash; 77\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e59 \u0026ndash; 74\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003e*: statistically significant; BP: Blood pressure; CI: Confidence interval; IQR: Inter-quartile range; LV: Left ventricular; Min: Minimum; Max: Maximum; p MC: Monte Carlo p-value; SD: Standard deviation; U, Z: Mann Whitney test statistics; significance level at p\u0026lt;0.05\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eApart from the eGFR using the MDRD formula which did not show any gender related statistically significant difference, all other selected biochemical parameters determined to all participants, namely serum levels of glucose and creatinine as well as activities of alanine and aspartate aminotransferases, were significantly higher in males compared to females, yet all were within the safely reported reference intervals for the chosen analytes\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable (2): Selected biochemical parameters and estimated GFR among the studied groups\u003c/strong\u003e\u003c/p\u003e\n\u003cdiv align=\"\"\u003e\n \u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"607\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 139px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eVariable\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 125px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eAll (n=240)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 127px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eMales (n=120)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 131px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eFemales (n=120)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cstrong\u003epMC\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"5\" valign=\"top\" style=\"width: 607px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eSerum glucose (mg/dL)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 139px;\"\u003e\n \u003cp\u003e\u0026nbsp;-Mean (95% CI) \u0026plusmn; SD.\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 125px;\"\u003e\n \u003cp\u003e89.49\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e(88.38 \u0026ndash; 90.6)\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026plusmn; 8.74\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 127px;\"\u003e\n \u003cp\u003e91.43\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e(89.83 \u0026ndash; 93.04)\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026plusmn; 8.86\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 131px;\"\u003e\n \u003cp\u003e87.55\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e(86.07 \u0026ndash; 89.03) \u0026plusmn; 8.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"3\" style=\"width: 85px;\"\u003e\n \u003cp\u003eU= 5347\u003c/p\u003e\n \u003cp\u003eZ= -3.45\u003c/p\u003e\n \u003cp\u003ep= 0.001*\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 139px;\"\u003e\n \u003cp\u003e\u0026nbsp;-Median (IQR)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 125px;\"\u003e\n \u003cp\u003e89 (16)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 127px;\"\u003e\n \u003cp\u003e91 (14.75)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 131px;\"\u003e\n \u003cp\u003e87.5 (13)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 139px;\"\u003e\n \u003cp\u003e\u0026nbsp;-Min. \u0026ndash; Max.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 125px;\"\u003e\n \u003cp\u003e70 \u0026ndash; 106\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 127px;\"\u003e\n \u003cp\u003e70 \u0026ndash; 106\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 131px;\"\u003e\n \u003cp\u003e71 \u0026ndash; 106\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"5\" valign=\"top\" style=\"width: 607px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"5\" valign=\"top\" style=\"width: 607px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eSerum creatinine (mg/dL)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 139px;\"\u003e\n \u003cp\u003e\u0026nbsp;-Mean (95% CI) \u0026plusmn; SD.\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 125px;\"\u003e\n \u003cp\u003e0.84\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e(0.81 \u0026ndash; 0.86)\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026plusmn; 0.18\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 127px;\"\u003e\n \u003cp\u003e0.94\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e(0.91 \u0026ndash; 0.97)\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026plusmn; 0.16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 131px;\"\u003e\n \u003cp\u003e0.74\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e(0.71 \u0026ndash; 0.76)\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026plusmn; 0.13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"3\" style=\"width: 85px;\"\u003e\n \u003cp\u003eU= 2632\u003c/p\u003e\n \u003cp\u003eZ= -8.61\u003c/p\u003e\n \u003cp\u003ep\u0026lt;0.001*\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 139px;\"\u003e\n \u003cp\u003e\u0026nbsp;-Median (IQR)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 125px;\"\u003e\n \u003cp\u003e0.8 (0.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 127px;\"\u003e\n \u003cp\u003e0.9 (0.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 131px;\"\u003e\n \u003cp\u003e0.7 (0.2)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 139px;\"\u003e\n \u003cp\u003e\u0026nbsp;-Min. \u0026ndash; Max.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 125px;\"\u003e\n \u003cp\u003e0.5 \u0026ndash; 1.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 127px;\"\u003e\n \u003cp\u003e0.5 \u0026ndash; 1.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 131px;\"\u003e\n \u003cp\u003e0.5 \u0026ndash; 1.0\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"5\" valign=\"top\" style=\"width: 607px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eEstimated-GFR (mL/min)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 139px;\"\u003e\n \u003cp\u003e\u0026nbsp;-Mean (95% CI) \u0026plusmn; SD.\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 125px;\"\u003e\n \u003cp\u003e102.24\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e(98.9 \u0026ndash; 105.57) \u0026plusmn; 26.22\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 127px;\"\u003e\n \u003cp\u003e102.4\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e(97.62 \u0026ndash; 107.18)\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026plusmn; 26.43\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 131px;\"\u003e\n \u003cp\u003e102.07\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e(97.35 \u0026ndash; 106.79) \u0026plusmn; 26.11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"3\" style=\"width: 85px;\"\u003e\n \u003cp\u003eU= 7193\u003c/p\u003e\n \u003cp\u003eZ= -0.01\u003c/p\u003e\n \u003cp\u003ep= 0.99\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 139px;\"\u003e\n \u003cp\u003e\u0026nbsp;-Median (IQR)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 125px;\"\u003e\n \u003cp\u003e99.65 (32.6)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 127px;\"\u003e\n \u003cp\u003e98.85 (30.9)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 131px;\"\u003e\n \u003cp\u003e101.8 (36.2)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 139px;\"\u003e\n \u003cp\u003e\u0026nbsp;-Min. \u0026ndash; Max.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 125px;\"\u003e\n \u003cp\u003e63.7 \u0026ndash; 230.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 127px;\"\u003e\n \u003cp\u003e69.6 \u0026ndash; 230.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 131px;\"\u003e\n \u003cp\u003e63.7 \u0026ndash; 170.8\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"5\" valign=\"top\" style=\"width: 607px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eSerum ALT (U/L)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 139px;\"\u003e\n \u003cp\u003e\u0026nbsp;-Mean (95% CI) \u0026plusmn; SD.\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 125px;\"\u003e\n \u003cp\u003e23.67\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e(22.01 \u0026ndash; 25.32)\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026plusmn; 13.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 127px;\"\u003e\n \u003cp\u003e27.64\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e(24.85 \u0026ndash; 30.43)\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026plusmn; 15.43\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 131px;\"\u003e\n \u003cp\u003e19.69\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e(18.18 \u0026ndash; 21.21) \u0026plusmn; 8.38\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"3\" style=\"width: 85px;\"\u003e\n \u003cp\u003eU= 5183\u003c/p\u003e\n \u003cp\u003eZ= -3.75\u003c/p\u003e\n \u003cp\u003ep\u0026lt;0.001*\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 139px;\"\u003e\n \u003cp\u003e\u0026nbsp;-Median (IQR)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 125px;\"\u003e\n \u003cp\u003e21 (14.75)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 127px;\"\u003e\n \u003cp\u003e22.5 (19.75)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 131px;\"\u003e\n \u003cp\u003e19.5 (11)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 139px;\"\u003e\n \u003cp\u003e\u0026nbsp;-Min. \u0026ndash; Max.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 125px;\"\u003e\n \u003cp\u003e6 \u0026ndash; 74\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 127px;\"\u003e\n \u003cp\u003e7 \u0026ndash; 74\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 131px;\"\u003e\n \u003cp\u003e6 \u0026ndash; 48\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"5\" valign=\"top\" style=\"width: 607px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eSerum AST (U/L)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 139px;\"\u003e\n \u003cp\u003e\u0026nbsp;-Mean (95% CI) \u0026plusmn; SD.\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 125px;\"\u003e\n \u003cp\u003e20.03\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e(19.08 \u0026ndash; 20.97) \u0026plusmn; 7.42\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 127px;\"\u003e\n \u003cp\u003e22.81\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e(21.4 \u0026ndash; 24.21) \u0026plusmn; 7.78\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 131px;\"\u003e\n \u003cp\u003e17.24\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e(16.18 \u0026ndash; 18.3)\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026plusmn; 5.88\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"3\" style=\"width: 85px;\"\u003e\n \u003cp\u003eU= 4140\u003c/p\u003e\n \u003cp\u003eZ= -5.7\u003c/p\u003e\n \u003cp\u003ep \u0026lt;0.001*\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 139px;\"\u003e\n \u003cp\u003e\u0026nbsp;-Median (IQR)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 125px;\"\u003e\n \u003cp\u003e19.5 (9.75)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 127px;\"\u003e\n \u003cp\u003e22 (11.5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 131px;\"\u003e\n \u003cp\u003e17 (8.75)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 139px;\"\u003e\n \u003cp\u003e\u0026nbsp;-Min. \u0026ndash; Max.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 125px;\"\u003e\n \u003cp\u003e7 \u0026ndash; 40\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 127px;\"\u003e\n \u003cp\u003e7 \u0026ndash; 40\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 131px;\"\u003e\n \u003cp\u003e7 \u0026ndash; 34\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003e*: statistically significant; ALT: Alanine aminotransferase; AST: Aspartate aminotransferase; GFR: Glomerular filtration rate; CI: Confidence interval; IQR: Inter-quartile range; LV: Left ventricular; Min: Minimum; Max: Maximum; p MC: Monte Carlo p-value; SD: Standard deviation; U, Z: Mann Whitney test statistics; significance level at p\u0026lt;0.05\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAs regards serum cTnT value among all the 240 individuals, 86 participants (35.8%) had serum cTnT below Level of detection (LOD). When divided according to gender; 27 (22.5%) out of the 120 male participants had serum cTnT below LOD and 59 (49.2%) out of the 120 females participants had serum cTnT below LOD (all were given a 3.0 ng/L value for sake of proper ranking of all distribution independent non-parametric ranking analyses that follows). Comparing serum cTnT among the two genders revealed a significantly higher level among male subjects (median = 5.5 ng/L) compared to female subjects (median = 3.05 ng/L), (Z=-4.324, p\u0026lt;0.001).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe 99\u003csup\u003eth\u003c/sup\u003e percentile URL of serum cTnT was first calculated among all of the 240 participants revealing an URL of 15.49 ng/L (95% CI: 11.1-20.1 ng/L)\u003c/p\u003e\n\u003cp\u003eThe URL of serum cTnT was then calculated for each gender (120 males and 120 female) independently. No outliers were found among each gender according to outlier detection method developed by Reed et al. (1971). Results showed an URL of 19.55 ng/L (95% CI: 10.89\u0026ndash;20.1 ng/L) among male participants and an URL of 12.58 ng/L (95% CI: 9.9\u0026ndash;12.6 ng/L)\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eWhen stratified according to an age cutoff value of 36 years, one group included 119 subjects aged less than 36 years and another group included 121 subjects aged 36 years or more. In the first group 70 out of 119 (58.8%) subjects had a serum cTnT below LOD while in the second group 16 out of 121 (13.2%) subjects had a serum cTnT below LOD (all were given a 3.0 ng/L value for sake of proper ranking of all distribution independent non-parametric ranking analyses that follows). Comparing serum cTnT among the two groups revealed a significantly higher serum cTnT level (median= 6.0 ng/L) among the group aged 36 years old or more compared to its level in the group aged less than 36 years (median= 3.0 ng/L), (U= 3027, Z=-7.96, P\u0026lt;0.001). Based on Reed et al. (1971) outlier detection method, one outlier result was found among the serum cTnT measurements of the group aged less than 36 years (20.1 ng/L) and another outlier in the group aged 36 years old or more (17.5 ng/L).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAccordingly, the 99\u003csup\u003eth\u003c/sup\u003e percentile URL of serum cTnT was calculated for each age group independently with and without excluding detected outliers. When including outliers (according to CLSI guideline that recommends a conservative policy of not deleting any values), the URL of cTnT was 18.1 ng/L (95% CI: 7.9\u0026ndash;20.1 ng/L) for the group less than 36 years old and an URL of 16.42 ng/L (95% CI: 12.08\u0026ndash;17.5 ng/L) for the group aged 36 years old or more.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eWhen excluding the detected outliers from both groups, the cTnT serum level revealed an URL of 10.0 ng/L (95% CI: 7.6\u0026ndash;10.1ng/L) for those aged less than 36 years old and an URL of 12.6 ng/L (95% CI: 11.3\u0026ndash;12.6 ng/L) for those aged 36 years or more\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eStill after excluding the detected outliers, serum cTnT was significantly higher in those aged 36 years or more (median= 6.0 ng/L) compared to its level in those aged less than 36 years (median= 3.0 ng/L), (U= 2905.5, Z=-8.068, p\u0026lt;0.001).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eWhen comparing serum cTnT level according to gender in both groups of participants divided according to an age value of 36 years old, significantly higher levels were found among males (median= 4.35 ng/L) compared to females (median= 3.0 ng/L) (U= 1161, Z= -3.315, p= 0.001) in the group aged less than 36 years old, which was not the case for those aged 36 years old or more, as no statistically significant difference was noted in its levels between males (median= 6.35 ng/L) and females (median= 5.2 ng/L) (U=413.5, Z=-1.854, p=0.061). \u0026nbsp;\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eIn order to verify the degree of imprecision of the hs-cTnT assay claimed by the manufacturer,\u0026nbsp;the daily triplicate \u0026times; 5 days design recommended by CLSI for verification of the manufacturer claimed precision for a pooled specimen\u0026nbsp;with a calculated mean value of 13.0 ng/L showed an overall mean value of 12.9 ng/L and a SD of 0.864 ng/L with a percent coefficient of variation (%CV) of 6.7%, a minimum value of 11.8 ng/L and a maximum value of 14.0 ng/L, with no outliers detected. In order to validate the assay\u0026rsquo;s degree of imprecision\u0026nbsp;at 10.0 ng/L (our lowest 99\u003csup\u003eth\u003c/sup\u003e percentile which is below the assay\u0026rsquo;s claimed LOQ of 13.0 ng/L), the daily duplicate \u0026times; 20 days design recommended by CLSI for precision validation was used and revealed for a pooled serum sample with a calculated mean value of 10.0 ng/L an overall measured mean value of 9.95 ng/L, a standard deviation of 0.761 ng/L, and a %CV of 7.7%, with a minimum value of 8.99 ng/L and a maximum value of 11.0 ng/L, with no outliers detected. Looking closely into the manufacturer precision assessment section of our kit, the tables showed that regarding the Cobas e411 analyzer %CV equal to 15% and 5.2% were calculated for intermediate precision at mean value of 7.5 ng/L and 13.5 ng/L, yet regarding the Cobas e601 module (immunoassay unit) of the Cobas 6000 modular analytical system (used in the current study), %CV equal to 8.6 and 5.2 were calculated for intermediate precision at mean values of 6.5 ng/L and 11 ng/L. Thus, the manufacturer adopted the higher CV% of less precise Cobas e411 to be the overall CV% used to determine its LOQ of the kit \u0026nbsp;, calming the limit of quantitation (LOQ) at 13.0 ng/L guarantee a (%CV) of \u0026lt;10% on all its platform when in reality as proved by the manufacturer own study and confirm by our precision study, \u0026nbsp;the cobas e601 module is in fact more precis than e411 and a lower LOQ of 10 \u0026nbsp;ng/L or even lower can be adopted and still \u0026nbsp;guarantee a (%CV) of \u0026lt;10% as recommended.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe rise of IHD, particularly acute myocardial infarction (AMI), among young and middle aged adults (18\u0026ndash;45 years) and its effect on personal and economic productivity, has driven worldwide efforts for decreasing its burden [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. Premature AMI refers to MI in men 55 years or less and in women 65 years or less. There are limited international studies on the relationship between risk factors (demographics, lifestyle factors, clinical risk factors and biomarkers) and premature MI. A study showed that these risk factors were higher among young versus elderly people [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. Furthermore, women remain the majority who die from cardiovascular disease (CVD), with an estimated 515,000 women each year diagnosed with coronary heart disease. Data indicate that CVD mortality among young women between the ages of 35 and 54 years is increasing due to some risk factors that are exclusive to women such as pregnancy-related complications, polycystic ovaries and oral contraceptives pills as well as other risk factors that are more prevalent in women than men such as mental stress induced ischemia, depression, and anxiety [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eAccording to the new universal definition, the only recommended diagnostic biomarkers for evaluation of myocardial injury and AMI are cardiac troponins (cTn) [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e], where cTnT immunoassay shows far better performance compared to cTnI immunoassays. The problem with the currently available cTn assays is their inability to discriminate between males and females, particularly among young and middle aged adults, concerning the 99th percentile URL that can safely discriminate an acute infarct from a non-infarct. The establishment and adoption of a more racial, gender and age-specific URL for cTn assays, particularly the more specific hs-cTnT assay, would be expected to decrease both over-diagnosis and under diagnosis of AMI, particularly in young and middle aged adults.\u003c/p\u003e \u003cp\u003eThe current study was done to establish a valid 99th percentile URL for serum cTnT among adult male and female subjects. There is much debate concerning both, the selection of a healthy reference population in determining cTns 99th percentile values. However, recent studies have shown that the selection criteria applied to define a healthy reference population may greatly influence the derived 99th percentile values for cTns. [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. Unfortunately to date, no evidence based guidelines or universal protocols have been formally implemented to support laboratories and manufacturers in establishing 99th percentile URLs for cTns [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. In multiple studies, several approaches have been proposed, ranging from data collection from self-reported questionnaires to screening with laboratory surrogate biomarkers, cardiac imaging techniques and other diagnostic tests, in order to evaluate the health status of individuals constituting a normal reference population [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eA study done by Sandoval and Apple suggested that the screening and enrolment of presumably healthy individuals into a study to determine the 99th percentile URL for cTn assay should minimally address the following; clinical history for known cardiovascular disease and medication usage, surrogate biomarkers for diabetes and renal dysfunction, appropriate non-parametric statistical analysis, possible inclusion of an imaging modality if financially feasible and a description of specimen type used [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe study was based on collecting serum samples from 240 apparently healthy young adult Egyptian volunteers aged 18\u0026ndash;45 years, divided into 120 males and 120 females for measuring serum cTnT using the 5th generation hs-cTnT assay. The current study identified that gender was an important factor influencing its serum concentrations. Comparing serum cTnT among the two genders revealed a significantly higher level among male compared to female subjects (Z= -4.324, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). Consequently, the derived 99th percentile value for cTnT in this study in female participants was lower (12.58 g/L) than that of male participants (19.55 ng/L). This observation was in agreement with Collinson et al whom reported a clear difference between men and women in the examined subgroups for the Roche hs-cTnT ECL immunoassay.[\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e] Several other studies support the existence of a discrepancy between percentile values of cTnT in men and women [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e, \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e, \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eStudies concerning gender-specific lower thresholds for women for the diagnosis of AMI have not shown consistent results. Shah et al. (2015) proposed that women-specific lower diagnostic thresholds for cTn may double the diagnosis of AMI in women, and identify those at high risk of re-infarction and death [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. On the other hand, a study by Gim\u0026eacute;nez et al. (2016) done on a larger sample size, demonstrated that gender-specific troponin thresholds did not improve diagnostic accuracy, and hence has proposed that the 99th percentile should remain the standard of care for both genders [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe potentially profound clinical importance of gender specific cutoff values would be evident when the use of gender specific diagnostic thresholds for cTns markedly increase the diagnosis of MI in women and improve the outcomes. In our study, the effect of age was obvious on serum cTnT levels when participants were divided according to an age cutoff value of 36 years, where serum cTnT levels were significantly lower in 119 subjects aged\u0026thinsp;\u0026lt;\u0026thinsp;36 years old compared to 121 subjects aged 36 years old or more (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001), with a proposed 99th percentile cutoff value of 18.1 ng/L and 16.42 ng/L respectively after including outliers according to the CLSI recommendations, and 10.0 ng/L and 12.6 ng/L respectively with excluding of outliers. Moreover, a serum cTnT level comparison across gender was done in both age groups revealing a significantly higher value of serum cTnT among males compared to females in those aged less than 36 years old (p\u0026thinsp;=\u0026thinsp;0.001). Such a gender related significant difference was lost in those aged 36 years old or more (p\u0026thinsp;=\u0026thinsp;0.061).\u003c/p\u003e \u003cp\u003eIn conclusion, a constant URL of 14.0 ng/L for the hs-cTnT assay in the diagnosis of AMI as proposed by the manufacturer in a study involving 533 healthy volunteers (age range: 20\u0026ndash;71 years) (95% confidence interval\u0026thinsp;=\u0026thinsp;12.7\u0026ndash;24.9 ng/L) does not reflect the 99th percentile value of a reference population with varied demographic characteristics. Instead, we propose that use of age and gender specific 99th percentile value as an URL for hs-cTnT assay would benefit the patient in early diagnosis of AMI and decrease false positive AMI diagnosis with the hs-cTnT assay, a problem with major clinical and public health ramifications. Further studies are needed to verify whether such age and gender specific cutoff values could improve the diagnostic performance of cTnT for AMI.\u003c/p\u003e "},{"header":"Abbreviations","content":"\u003cp\u003eCK-MB Muscle brain fraction of creatine kinase\u003c/p\u003e\n\u003cp\u003eCLSI Clinical Laboratory Standard Institute \u003c/p\u003e\n\u003cp\u003eFAG Antigen \u0026ndash;binding fragment \u003c/p\u003e\n\u003cp\u003ecTn Cardiac troponins\u003c/p\u003e\n\u003cp\u003eC-TnC C-terminal domains of TnC\u003c/p\u003e\n\u003cp\u003ehs-cTnT High sensitive-Cardiac troponin-T \u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics declarations\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflicts of interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNone to declare by the authors of this manuscript\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthical approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was performed at the Medical Research Institute hospital. approval was granted by the Ethics committee of the Medical Research Institute, Alexandria University (approval number: E/C.S/N.T84/2019). All volunteers gave informed and written consent.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors have no relevant financial or non-financial interests to disclose.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor Contribution\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA.T. and A.R. contributed to the conception , design of the work; the acquisition ,analysis, and interpretation; M. L. supervised the case selection and conducted the clinical part; A.A and A.T wrote and revised the manuscript; All authors have reviewed and approved the final version of the manuscript.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eChandrasekhar, J., Gill, A., \u0026amp; Mehran, R. (2018). Acute myocardial infarction in young women: current perspectives. International journal of women\u0026apos;s health, 10, 267-284.\u003c/li\u003e\n \u003cli\u003eMorrow, D. A., Cannon, C. P., Jesse, R. L., Newby, L. K., Ravkilde, J., Storrow, A. B. . . . \u0026amp; Christenson, R. H. (2007). National Academy of Clinical Biochemistry Laboratory Medicine Practice Guidelines: Clinical characteristics and utilization of biochemical markers in acute coronary syndromes. Circulation, 115(13), e356-375.\u003c/li\u003e\n \u003cli\u003eThygesen, K., Alpert, J. S., Jaffe, A. S., Chaitman, B. R., Bax, J. J., Morrow, D. A., \u0026amp; White, H. D. (2018). Fourth Universal Definition of Myocardial Infarction (2018). Journal of the American College of Cardiology, 25285.\u003c/li\u003e\n \u003cli\u003eGiannitsis, E., Kurz, K., Hallermayer, K., Jarausch, J., Jaffe, A. S., \u0026amp; Katus, H. A. (2010). Analytical validation of a high-sensitivity cardiac troponin T assay. Clinical chemistry, 56(2), 254-261.\u003c/li\u003e\n \u003cli\u003eHerman, D. S., Kavsak, P. A., \u0026amp; Greene, D. N. (2017). Variability and Error in Cardiac Troponin Testing: An ACLPS Critical Review. American journal of clinical pathology, 148(4), 281-295.\u003c/li\u003e\n \u003cli\u003eApple, F. S., \u0026amp; Collinson, P. O. (2012). Analytical characteristics of high-sensitivity cardiac troponin assays. Clinical chemistry, 58(1), 54-61.\u003c/li\u003e\n \u003cli\u003eApple, F. S., Sandoval, Y., Jaffe, A. S., \u0026amp; Ordonez-Llanos, J. (2017). Cardiac Troponin Assays: Guide to Understanding Analytical Characteristics and Their Impact on Clinical Care. Clinical chemistry, 63(1), 73.\u003c/li\u003e\n \u003cli\u003ede Lemos, J. A. (2013). Increasingly sensitive assays for cardiac troponins: a review. Journal of the American medical association, 309(21), 2262-2269.\u003c/li\u003e\n \u003cli\u003eKimenai, D. M., Janssen, E., Eggers, K. M., Lindahl, B., den Ruijter, H. M., Bekers, O. . . . \u0026amp; Meex, S. J. R. (2018). Sex-Specific Versus Overall Clinical Decision Limits for Cardiac Troponin I and T for the Diagnosis of Acute Myocardial Infarction: A Systematic Review. Clinical chemistry, 64(7), 1034-1043.\u003c/li\u003e\n \u003cli\u003eShah, A. S. V., Ferry, A. V., \u0026amp; Mills, N. L. (2017). Cardiac Biomarkers and the Diagnosis of Myocardial Infarction in Women. Current cardiology reports, 19(5), 40-40.\u003c/li\u003e\n \u003cli\u003eRomiti, G. F., Cangemi, R., Toriello, F., Ruscio, E., Sciomer, S., Moscucci, F. . . . \u0026amp; Raparelli, V. (2019). Sex-Specific Cut-Offs for High-Sensitivity Cardiac Troponin: Is Less More? Cardiovascular therapeutics, 2019, 9546931-9546931.\u003c/li\u003e\n \u003cli\u003eHorowitz, G. L. (2008). Reference Intervals: Practical Aspects. Electronic journal of the international federation of clinical chemistry, 19(2), 95-105.\u003c/li\u003e\n \u003cli\u003eHorowitz, G. L., Altaie, S., Boyd, J. C., Ceriotti, F., Garg, U., Horn, P. . . . \u0026amp; Zakowski, J. (2008). Defining, establishing, and verifying reference intervals in the clinical laboratory; approved guideline vol. 28. 3\u003csup\u003erd\u003c/sup\u003e ed. CLSI document E28\u0026ndash;A3. Wayne, PA: Clinical and Laboratory Standards Institute.\u003c/li\u003e\n \u003cli\u003eTanindi, A., \u0026amp; Cemri, M. (2011). Troponin elevation in conditions other than acute coronary syndromes. Vascular health and risk management, 7, 597-603.\u003c/li\u003e\n \u003cli\u003eMcKie, P. M., Heublein, D. M., Scott, C. G., Gantzer, M. L., Mehta, R. A., Rodeheffer, R. J. . . . \u0026amp; Jaffe, A. S. (2013). Defining High-Sensitivity Cardiac Troponin Concentrations in the Community. Clinical chemistry, 59(7), 1099.\u003c/li\u003e\n \u003cli\u003ePuri, B. (2002). SPSS in Practice 2\u003csup\u003end\u003c/sup\u003e ed. An illustrated guide: Taylor \u0026amp; Francis.\u003c/li\u003e\n \u003cli\u003eDaly, L., \u0026amp; Bourke, G. J. (2008). Interpretation and Uses of Medical Statistics. United States: Wiley.\u003c/li\u003e\n \u003cli\u003eReed, A. H., Henry, R. J., \u0026amp; Mason, W. B. (1971). Influence of statistical method used on the resulting estimate of normal range. Clinical chemistry, 17(4), 275-284.\u003c/li\u003e\n \u003cli\u003eBenjamin, E. J., Blaha, M. J., Chiuve, S. E., Cushman, M., Das, S. R., Deo, R. . . . \u0026amp; Stroke Statistics, S. (2017). Heart Disease and Stroke Statistics-2017 Update: A Report From the American Heart Association. Circulation, 135(10), e146-e603.\u003c/li\u003e\n \u003cli\u003eDugani, S. B., Ayala Melendez, A. P., Reka, R., Hydoub, Y. M., McCafferty, S. N., Murad, M. H. . . . \u0026amp; Mora, S. (2019). Risk factors associated with premature myocardial infarction: a systematic review protocol. British medical journal open, 9(2), e023647-e023647.\u003c/li\u003e\n \u003cli\u003eMehta, P. K., Wei, J., \u0026amp; Wenger, N. K. (2015). Ischemic heart disease in women: a focus on risk factors. Trends in cardiovascular medicine, 25(2), 140-151.\u003c/li\u003e\n \u003cli\u003eAw, T. C., Huang, W. T., Le, T. T., Pua, C. J., Ang, B., Phua, S. K. . . . \u0026amp; Chin, C. (2018). High-Sensitivitycardiac Troponinsin Cardio-Healthy Subjects: A Cardiovascular Magnetic Resonance Imaging Study. Scientific reports, 8(1), 15409-15409.\u003c/li\u003e\n \u003cli\u003eKozinski, M., Krintus, M., Kubica, J., \u0026amp; Sypniewska, G. (2017). High-sensitivity cardiac troponin assays: From improved analytical performance to enhanced risk stratification. Critical Reviews in Clinical Laboratory Sciences, 54(3), 143-172.\u003c/li\u003e\n \u003cli\u003eKrintus, M., Kozinski, M., Boudry, P., Lackner, K., Lefevre, G., Lennartz, L. . . . \u0026amp; Sypniewska, G. (2015). Defining normality in a European multinational cohort: Critical factors influencing the 99th percentile upper reference limit for high sensitivity cardiac troponin I. International journal of cardiology, 187, 256-263.\u003c/li\u003e\n \u003cli\u003eCollinson, P. O., Heung, Y. M., Gaze, D., Boa, F., Senior, R., Christenson, R., \u0026amp; Apple, F. S. (2020). Influence of Population Selection on the 99th Percentile Reference Value for Cardiac Troponin Assays. Clinical chemistry, 58(1), 219-225.\u003c/li\u003e\n \u003cli\u003eKimenai, D. M., Henry, R. M., van der Kallen, C. J., Dagnelie, P. C., Schram, M. T., Stehouwer, C. D. . . . \u0026amp; Meex, S. J. (2016). Direct comparison of clinical decision limits for cardiac troponin T and I. Heart, 102(8), 610-616.\u003c/li\u003e\n \u003cli\u003eMueller, T., Egger, M., Leitner, I., Gabriel, C., Haltmayer, M., \u0026amp; Dieplinger, B. (2016). Reference values of galectin-3 and cardiac troponins derived from a single cohort of healthy blood donors. Clinica chimica act, 456, 19-23.\u003c/li\u003e\n \u003cli\u003eYang, S., Huai, W., Qiao, R., Cui, L., Liu, G., Wu, J. . . . \u0026amp; Zhang, J. (2016). Age and Gender Tailored Cut-off Value of hs-cTnT Contributes to Rapidly Diagnose Acute Myocardial Infarction in Chest Pain Patients. Clinical laboratory, 62(8), 1451-1459.\u003c/li\u003e\n \u003cli\u003eMonneret, D., Gellerstedt, M., \u0026amp; Bonnefont-Rousselot, D. (2018). Determination of age- and sex-specific 99th percentiles for high-sensitive troponin T from patients: an analytical imprecision- and partitioning-based approach. Clinical chemistry and laboratory medicine, 56(5), 685-696.\u003c/li\u003e\n \u003cli\u003eUngerer, J. P. J., Tate, J. R., \u0026amp; Pretorius, C. J. (2020). Discordance with 3 Cardiac Troponin I and T Assays: Implications for the 99th Percentile Cut-off. Clinical chemistry, 62(8), 1106-1114.\u003c/li\u003e\n \u003cli\u003eWelsh, P., Preiss, D., Shah, A. S. V., McAllister, D., Briggs, A., Boachie, C. . . . \u0026amp; Sattar, N. (2020). Comparison between High-Sensitivity Cardiac Troponin T and Cardiac Troponin I in a Large General Population Cohort. Clinical chemistry, 64(11), 1607-1616.\u003c/li\u003e\n \u003cli\u003eShah, A. S. V., Griffiths, M., Lee, K. K., McAllister, D. A., Hunter, A. L., Ferry, A. V. . . . \u0026amp; Mills, N. L. (2015). High sensitivity cardiac troponin and the under-diagnosis of myocardial infarction in women: prospective cohort study. British medical journal, 350, g7873.\u003c/li\u003e\n \u003cli\u003eRubini Gimenez, M., Twerenbold, R., Boeddinghaus, J., Nestelberger, T., Puelacher, C., Hillinger, P. . . . \u0026amp; Mueller, C. (2016). Clinical Effect of Sex-Specific Cut-off Values of High-Sensitivity Cardiac Troponin T in Suspected Myocardial Infarction. Journal of the American Medical Association cardiology, 1(8), 912-920.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Acute myocardial infarction, high sensitive cTnT, 99th percentile URL","lastPublishedDoi":"10.21203/rs.3.rs-5299564/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5299564/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e \u003cp\u003eCardiac troponins are the preferred biomarkers for the diagnosis of acute myocardial infarction (AMI). The stable nature of cardiac troponin T (cTnT) in the circulation and the worldwide available single standardized assay make it a more precise biomarker of AMI. The manufacturer\u0026rsquo;s proposed upper reference limit (URL) for the high sensitive (hs)-cTnT assay does not take into consideration patients\u0026rsquo; gender, age or race. The study aimed at establishing and comparing gender-specific upper reference limit for cardiac troponin-T among apparently healthy young adult Egyptians.\u003c/p\u003e\u003ch2\u003eSubjects and methods\u003c/h2\u003e \u003cp\u003e240 adult Egyptians (120 males and 120 females) participated in this study. Serum cTnT was determined using a commercially available hs-cTnT electrochemiluminescent immunoassay. The gender related 99th percentile values were then calculated to represent the URLs for cTnT according to the CLSI and IFCC approved guidelines.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eSerum cTnT was significantly higher in males compared to females (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). The 99th percentile URL for cTnT in females (12.58 ng/L) was lower than that of males (19.55 ng/L). Upon dividing them according to an age cutoff value of 36 years, serum cTnT level was significantly lower among those aged\u0026thinsp;\u0026lt;\u0026thinsp;36 years old (n\u0026thinsp;=\u0026thinsp;119) compared to those aged 36 years old or more (n\u0026thinsp;=\u0026thinsp;121) (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001), with a proposed 99th percentile URL after including outliers of 18.1 ng/L for the former and 16.42 ng/L for the latter, while after excluding outliers the URL was 10.0 ng/L for the former and 12.6 ng/L for the latter. Moreover, a significantly higher serum cTnT value among males compared to females was only noticed in those aged less than 36 years old (p\u0026thinsp;=\u0026thinsp;0.001).\u003c/p\u003e\u003ch2\u003eConclusion:\u003c/h2\u003e \u003cp\u003eAn adult patient in early diagnosis of AMI by increasing both assay\u0026rsquo;s specificity among adult The use of age and gender specific 99th percentile value as an URL of hs-cTnT assay would benefit males (decreasing over-diagnosis) and assay\u0026rsquo;s sensitivity among adult females (decreasing under-diagnosis).\u003c/p\u003e","manuscriptTitle":"Establishment of gender related 99th percentile values for cardiac troponin-T among young and middle-aged adult Egyptians ","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-10-25 06:09:04","doi":"10.21203/rs.3.rs-5299564/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"a4057dfb-eaa5-4602-a9dd-1bbd7024c919","owner":[],"postedDate":"October 25th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-02-28T07:38:57+00:00","versionOfRecord":[],"versionCreatedAt":"2024-10-25 06:09:04","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-5299564","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5299564","identity":"rs-5299564","version":["v1"]},"buildId":"7rjqhiLT3MXkJMwkYKINL","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}