Analysis of QuantiFERON-TB Gold Plus assay in Children and Adolescents with Latent and Active Tuberculosis in China

Analysis of QuantiFERON-TB Gold Plus assay in Children and Adolescents with Latent and Active Tuberculosis in China | 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 Analysis of QuantiFERON-TB Gold Plus assay in Children and Adolescents with Latent and Active Tuberculosis in China Huiwen Zheng, Yanhong Yu, Yonghong Wang, Yajie Guo, Yang Wang, and 6 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5399017/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 4 You are reading this latest preprint version Abstract Objective To evaluate the accuracy of QuantiFERON-TB Gold Plus (QFT-Plus) assay, and analyze the quantitative interferon gamma (IFN-γ) responses to tuberculosis (TB) antigens and mitogen in children and adolescents with active TB and latent tuberculosis infection (LTBI) in China. Methods A retrospective study was conducted among patients <25 years old with suspected active TB or screened for LTBI. All patients underwent QFT-Plus tests at Beijing Children’s Hospital and Shenyang Chest Hospital from August 2022 to March 2024. Demographic and clinical data were extracted from their electronic medical record. Results A total of 18482 patients were recruited, including 179 (1.0%) patients with active TB disease, 334 (1.8%) LTBI and 17969 (97.2%) non-TB disease. The 5.8% (176/18482) patients had indeterminate results. The overall sensitivity for active TB was 83.4%, and specificity was 98.0%. The percent agreement between TB1 and TB2 was 90.3%. The IFN-γ production in response to mitogen and TB antigens observed among children <1 year of age was lower than that among other age groups. There was significant positive correlation between age and IFN-γ responses to mitogen, but negative correlation between age and IFN-γ responses to TB1 and TB2 antigen. Besides, there was no significant difference in response to QFT-Plus TB antigens in active TB and LTBI cases. Conclusion QFT-Plus assay is accurate in children and adolescents with active TB. IFN-γ responses to mitogen and MTB antigens are significantly affected by age. The new antigen tube TB2 increases the assay sensitivity. Tuberculosis Children Interferon gamma release assay QuantiFERON Plus Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Introduction Tuberculosis (TB), caused by Mycobacterium tuberculosis (MTB), is one of the leading causes of death worldwide, with approximately 10.6 million incident cases in 2022 [ 1 ]. Pediatric TB accounted for 12% of the total cases, bearing a substantial part of the TB epidemic [ 1 ]. Almost one-quarter of the world’s population is latently infected with MTB, and the risk of progression to TB disease is much higher in infants (30%-40%) and children (10%-20%) than in adults within the first 2 years after infection, constituting a large reservoir that sustains TB disease [ 2 – 4 ]. Therefore, early detection and initiation preventive therapy for MTB infection are key strategies in controlling pediatric TB. Moreover, due to the nonspecific clinical presentation, paucibacillary nature of TB, extrapulmonary localization and difficulties in obtaining sputum samples, the diagnosis of pediatric TB is hampered [ 5 , 6 ]. Current guidelines recommend a combination of clinical, microbiological, radiological, and immunological approaches to improve the diagnosis of pediatric TB [ 7 – 9 ]. Interferon gamma release assays (IGRAs) are immunoassays based on the in vitro detection of interferon gamma (IFN-γ) produced by specifically sensitized T cells, following stimulation with MTB specific antigens, which contributes to identify individuals infected with MTB, and aid to diagnosis of pediatric TB disease [ 2 , 10 ]. Recently, the 4th-generation QuantiFERON-TB Gold Plus (QFT-Plus) (QIAGEN, Germantown, Maryland, USA) IGRA has been introduced. Different from its predecessor QuantiFERON-TB Gold In Tube (QFT-IT), QFT-Plus has no TB7.7 peptides in its antigenic components, namely first antigen tube (TB1) directed at CD4 + T cells, but added a second antigen tube (TB2) containing additional shorter ESAT-6 and CFP-10 peptides to elicit both CD4 + and CD8 + T cell responses, hoping to improve the sensitivity for the detection of MTB infection [ 11 , 12 ]. As there are no data about QFT-Plus performance in children and adolescents with active TB and latent tuberculosis infection (LTBI) in China, we performed this study to evaluate the accuracy of QFT-Plus assay, and analyze the quantitative IFN-γ responses to TB antigens and mitogen according to age, disease diagnosis and anatomic sites, which will provide the basis for clinical diagnosis and treatment. Methods Study design This was a retrospective study for patients <25 years old with suspected active TB (symptomatic patients) and otherwise screened for LTBI, received QFT-Plus tests at Beijing Children’s Hospital and Shenyang Chest Hospital from August 2022 to March 2024. Demographic and clinical data were extracted from their electronic medical record, including age, sex, QFT-Plus results, microbiologic findings and final diagnosis. Patient categories The diagnosis of TB disease is based on epidemiologic, clinical, radiologic, and microbiologic findings [ 13 ]. According to the composite reference standard, patients with TB disease were categorized into (1) bacteriologically confirmed TB: positive results of smear microscopy or culture or molecular tests; (2) clinically diagnosed TB: at least 1 symptom and sign, X-ray abnormalities suggestive of tuberculosis, and at least 1 of the following: clinical and radiologic improvement after anti-TB treatment, exposure history of active TB, positive results of tuberculin skin test, or interferon-γ release assay. Based on the anatomic site, the patients with TB disease were categorized into (1) pulmonary tuberculosis (PTB): any bacteriologically confirmed or clinically diagnosed case of TB involving the lung parenchyma or the tracheobronchial tree, and miliary TB is classified as PTB (2) extrapulmonary tuberculosis (EPTB): any bacteriologically confirmed or clinically diagnosed case of TB involving organs other than the lungs (e.g. pleura, peripheral lymph nodes, abdomen, genitourinary tract, skin, joints and bones, meninges) [ 14 ]. (3) Combined tuberculosis: concurrent pulmonary and extrapulmonary TB. 14 Diagnosis of LTBI was based on positive QFT-Plus and absence of any clinical, microbiological, and radiological features that would suggest active disease [ 15 ]. non-TB: cases with other diagnosis. QFT-Plus assay According to the manufacturer's instructions, 1 ml of venipuncture blood collected in lithium heparin tubes was transferred into each of the four separate test tubes: a negative control (nil) tube, a positive control (mitogen) tube and two antigen tubes (TB1 and TB2). Each tube was incubated for 16 to 24 h at 37°C, followed by centrifugation for 15 min at 2,000 xg to collect supernatants and assess IFN-γ levels (IU/ml) by enzyme-linked immunosorbent assay. The results were considered positive if either the IFN-γ values of TB1-Nil or TB2-Nil were ≥ 0.35 IU/mL and ≥ 25% of the Nil value. Results showing a nil value of >8.0 IU/ml or a mitogen value of <0.5 IU/ml were considered indeterminate. Statistical analysis Categorical variables are reported as absolute frequencies and percentages. Sensitivity was calculated based on the proportion of positive QFT-Plus results with 95% CI, indeterminate results were excluded from this particular analysis. Quantitative background-corrected antigen-stimulated IFN-γ responses in QFT-Plus assay among subgroups were compared with Kruskal-Wallis tests. Total agreement and Cohen’s kappa coefficient (k) were used to quantify concordance between TB1 and TB2 results. Statistical analysis was performed using GraphPad Prism v8.0.1 (GraphPad, San Diego, CA, USA), with statistical significance defined as a P value of <0.05. Results Study population A total of 18482 patients were recruited, including 179 (1.0%) patients with active TB disease, 334 (1.8%) LTBI and 17969 (97.2%) non-TB disease (Fig. 1 ). Of all the patients tested by QFT-Plus assay, 491 (2.7%) were positive, 16915 (91.5%) were negative, and 1076 (5.8%) had indeterminate results. Of the 513 patients with TB disease and LTBI, there were 125 (24.4%, 125/513) adolescents (≥ 18 years of age) and 388 (75.6%, 388/513) children (<18 years of age), including 11/388 (2.8%) aged <1 year, 72/388 (18.6%) aged 1 to 5 years, 109/388 (28.1%) aged 6 to 10 years, and 196/388 (50.5%) aged 11 to 17 years. Of the 179 active TB cases, 86 (48.0%, 86/179) cases were bacteriologically confirmed TB and 93 (52.0%, 93/179) cases were clinically confirmed TB. Besides, 108 (60.3%, 108/179) PTB, 38 (21.2%, 38/179) EPTB and 33 (18.4%, 33/179) combined TB were confirmed according to anatomic sites (Table 1 ). Table 1 Study population with TB disease and LTBI Parameter Total no. (%) (n = 513) No. bacteriologically confirmed TB (%) (n = 86) No. clinically confirmed TB (%) (n = 93) No. LTBI (%) (n = 334) Gender Male 263 (51.3) 45 (52.3) 56 (60.2) 162 (48.5) Female 250 (48.7) 41 (47.7) 37 (39.8) 172 (51.5) Age <1 year 11 (2.1) 7 (8.1) 2 (2.2) 2 (0.6) 1–5 years 72 (14.0) 8 (9.3) 13 (14.0) 51 (15.3) 6–10 years 109 (21.2) 11 (12.8) 19 (20.4) 79 (23.7) 11–17 years 196 (38.2) 14 (16.3) 29 (31.2) 153 (45.8) 18–24 years 125 (24.4) 46 (53.5) 30 (32.3) 49 (14.7) Patient group PTB only 108 (21.1) 55 (64.0) 53 (57.0) - EPTB only 38 (7.4) 12 (14.0) 26 (28.0) - Combined TB 33 (6.4) 19 (22.1) 14 (15.1) - Accuracy of QFT-Plus and agreement between TB1 and TB2 Among the 179 active TB patients tested by QFT-Plus assay, 146 (81.6%) were positive, 29 (19.9%) were negative, and 4 (2.2%) scored indeterminate results (insufficient mitogen response). As shown in Table 2 , the overall sensitivity for active TB was 83.4% (77.9%-89.0%), and specificity was 98.0% (97.8%-98.2%). Except for the subgroup of patients with combined TB (71.9% [55.4%-88.3%]) and patients 78% among all subgroups analyzed, but no significant difference was observed among age groups. Among subgroup with final diagnoses of active TB, QFT-Plus showed higher sensitivity in clinically confirmed TB patients than in bacteriologically confirmed TB patients (87.8% vs 78.8%), but this was not statistically significant. Similar sensitivity of QFT-Plus was observed in the subgroup of patients with PTB and EPTB, but higher than that and in subgroups of combined TB (86.0% vs 86.1% vs 71.9%). After excluding the indeterminate results, 175 active TB cases with QFT-Plus results were available (Table 3 ). 131 cases were identified by both TB1 and TB2, 5 identified by TB1 only and 12 identified by TB2 only, with percent agreement between TB1 and TB2 was 90.3% and a Cohen’s Kappa efficient of 0.700. Moderate agreement between TB1 and TB2 was observed among EPTB (κ = 0.583) and clinically confirmed TB group (κ = 0.585). The agreement was substantial among PTB (κ = 0.706) and combined TB (κ = 0.776), and almost perfect among bacteriologically confirmed TB (κ = 0.820) cases. Table 2 Sensitivity of QFT plus assay in patients with active TB Patient group No. of patients No. (%) QFT-Plus Sensitivity (95% CI) (%) P value Positive Negative Indeterminate All active TB 179 146 (81.6) 29 (19.9) 4 (2.2) 83.4 (77.9–89.0) Composite reference standard 0.111 Bacteriologically confirmed TB 86 67 (77.9) 18 (20.9) 1 (1.2) 78.8 (70.0-87.7) Clinically confirmed TB 93 79 (84.9) 11 (11.8) 3 (3.2) 87.8 (80.9–94.7) Anatomic site 0.151 PTB only 108 92 (85.2) 15 (13.9) 1 (0.9) 86.0 (79.3–92.7) EPTB only 38 31 (81.6) 5 (13.2) 2 (5.3) 86.1 (74.2–98.0) Combined TB 33 23 (69.7) 9 (27.3) 1 (3.0) 71.9 (55.4–88.3) Age 0.255 <1 year 9 4 (44.4) 3 (33.3) 2 (22.2) 57.1 (7.7-106.6) 1–5 years 21 16 (76.2) 3 (14.3) 2 (9.5) 84.2 (66.2-102.3) 6–10 years 30 25 (83.3) 5 (16.7) 0 (0) 83.3 (69.2–97.5) 11–17 years 43 34 (79.0) 9 (20.9) 0 (0) 79.0 (66.4–91.7) 18–24 years 76 67 (88.2) 9 (11.8) 0 (0) 88.2 (80.7–95.6) Gender 0.905 Male 101 81 (80.2) 17 (16.8) 3 (3.0) 80.2 (72.3–88.1) Female 78 65 (83.3) 13 (16.7) 1 (1.3) 83.3 (73.7–90.9) Table 3 Test agreement between TB1 and TB2 in children with active TB Category Total no. Mean No. with TB1/TB2 results Percent agreement Kappa value TB1 (IU/ml) TB2 (IU/ml) +/- +/+ -/+ -/- ATB 175 3.01 3.45 5 131 12 27 90.3% 0.700 PTB only 107 3.22 3.63 3 84 6 14 91.6% 0.706 EPTB only 36 2.45 3.23 1 26 4 5 86.1% 0.583 Combined TB 32 2.90 3.12 1 21 2 8 90.6% 0.776 Bacteriologically confirmed TB 85 2.82 3.45 1 65 4 15 94.1% 0.820 Clinically confirmed TB 90 3.29 3.56 4 66 8 12 86.7% 0.585 Quantitative QFT-Plus responses to TB antigens and mitogen according to diagnosis IFN-γ levels in response to mitogen and nil-corrected TB antigens in different diagnostic groups are shown in Fig. 2 . Regarding disease localization, median IFN-γ responses to mitogen were lower in cases of EPTB (7.79 IU/ml) than in cases of PTB (8.58 IU/ml) and combined TB (8.36 IU/ml), although the difference was not statistically significant. Though the TB2 levels in the QFT-Plus antigen tubes were higher than the TB1 levels in children with active TB (Table 3 ), no significant differences in IFN-γ production in response to TB1 and TB2 antigens were observed among subgroup with final diagnoses ( P = 0.57 for TB1, P = 0.17 for TB2, respectively) and subgroup of patients with disease localization ( P = 0.54 for TB1, P = 0.76 for TB2, respectively). Quantitative QFT-Plus responses to TB antigens and mitogen according to age As shown in Fig. 3 , IFN-γ production in response to mitogen observed among children <1 year of age (median of 5.72 IU IFN-γ/ml) was significantly lower than that among children 6 to 10 years of age (median of 8.96 IU IFN-γ/ml, P <0.01), 11 to 17 years of age (median of 9.32 IU IFN-γ/ml, P <0.001), and youth 18 to 25 years (median of 9.03 IU IFN-γ/ml, P <0.01). Besides, children aged 1 to 5 years had significantly lower IFN-γ response to mitogen (median of 8.00 IU IFN-γ/ml) than that in children 11 to 17 years of age (median of 9.32 IU IFN-γ/ml, P <0.05). The median IFN-γ responses to TB1 antigen was significantly lower in children <1 year of age (median of 1.38 IU IFN-γ/ml) than in children 1 to 5 years of age (median of 3.95 IU IFN-γ/ml, P <0.05). And significant difference in IFN-γ production in response to TB2 antigen was observed among age subgroups ( P = 0.04). Linear regression analysis showed that there was significant positive correlation between age and IFN-γ responses to mitogen (Pearson’s correlation coefficient r = 0.1660 [95% CI, 0.08054 to 0.2490]; P <0.01), but negative correlation between age and IFN-γ responses to TB1 (Pearson’s r =-0.1030 [95% CI, -0.1879 to -0.01662]; P <0.05) and TB2 antigen (Pearson’s r =-0.08818 [95% CI, -0.1734 to -0.001625]; P <0.05) (Fig. 4 ). Quantitative values of TB Ag to discriminate active TB from LTBI The median mitogen response value for LTBI (9.20 IU/ml) was higher with respect to TB cases (8.37 IU/ml), but there was no significant difference (Fig. 5 ). The mean values of TB1 and TB2 antigens in active TB (TB1: 3.44 IU/ml; TB2: 3.81 IU/ml) were higher than those in LTBI cases (TB1: 3.32 IU/ml; TB2: 3.44 IU/ml), respectively, but the difference was not statistically significant (Fig. 2 ). Besides, there was no significant difference in response to QFT-Plus TB antigens in active TB and LTBI cases according to age groups (Fig. 5 ). Discussion This study is preliminary to evaluate the performance of QFT-Plus in children and adolescents in China. We found that 5.8% (1076/18482) patients evaluated with QFT-Plus had indeterminate results, which is smaller than what has been reported from our previous studies on QFT-IT in children [ 16 ]. A recent multicenter study by Buonsenso et al. revealed an overall rate of indeterminate QFT-Plus results of 3.1% (11 of 358 children) [ 17 ], and their another research reported 2.5% (5/198) children evaluated with QFT-Plus had an indeterminate result [ 15 ]. And Nguyen et al. found that only 1/222 (0.45%) children had indeterminate QFT-Plus results in Vietnam [ 18 ], confirming that QFT-Plus is effective in children. Among the 4 cases (≤ 3 years) with indeterminate results in patients with active TB, one had congenital immunodeficiency, one had bacterial infections, and 2 had miliary and/or central nervous system (CNS) TB, suggesting that young age, CNS disease, and ongoing infection may be a stronger driver of indeterminate test results [ 19 – 21 ]. To our knowledge, little studies have evaluated the performance of QFT-Plus in children with TB disease so far. Our data showed the overall sensitivity and specificity was 83.4% and 98.0%, respectively, comparebale to most studies. The currently largest multicenter study conducted in Europe reported the overall sensitivity and specificity of QFT-Plus was 83.8% and 90.1% in 358 children with active TB, respectivley [ 17 ], and another study from the same group found a sensitivity of 83.3% in 12 children received a final diagnosis of active TB [ 15 ]. Another larger muticenter study with 158 pediatric TB disease conducted in Spain, realved a sensitivity of the assay was 82.9% [ 22 ], another two studies from the same group reported the sensitivity of 87.3% in 102 paediatric TB cases [ 23 ], and 83.6% in 189 pediatric TB disease [ 24 ]. However, one study in Vietnam reported the sensitivity of the assay was only 54% in 33 children with confirmed TB disease, while 84.2% in patients with isolated PTB (n = 19), and 14.3% in patients with EPTB (n = 7) and concomitant PTB and EPTB, respectively (n = 7) [ 18 ]. The sensitivity in PTB is comparable with our founding of 86.0%, indicating QFT-Plus had a rather good sensitivity in patients with exclusive PTB. The difference in sensitivity of QFT-Plus on EPTB may be depend on the extra-pulmonary TB site, which performs worse in patients with miliary and/or CNS TB, as well as in immunocompromised children [ 17 ]. 17 So as has been claimed, QFT-Plus assays has not enhanced sensitivity than previous generation IGRAs [ 17 , 24 , 25 ]. Subgroup analyses demonstrated that the sensitivity of QFT-Plus was higher in clinically confirmed TB than that in bacteriologically confirmed TB cases, which was consistent with a muticenter study in Spain [ 22 ], but none were statistically significant. Howerver, another study by the same group showed the opposite results [ 24 ]. So whether there was a relationship between antigenic load and the magnitude of IFN-γ responses, need further to be confirmed by larger size of these subgroups. We found the TB1/TB2 agreement was 90.3%, lower than that reported in Vietnam (96.4%) [ 18 ]. According to previous research [ 26 ], the TB2 levels in the QFT-Plus antigen tubes were higher than the TB1 levels. And 6.9% (12/175) patients with negative responses in the TB1 tube were identified by TB2 tube, indicating that TB2 stimulation induces a CD8 T-cell response that are in addition to CD4-response. The analyses of quantitative mitogen and antigen-induced IFN-γ responses were lower in children < 1 year of age, a group at higher risk of indeterminate assay results, suggesting that they are unable to produce a response to ensure a valid QFT-Plus result. Linear regression analysis demonstrated that IFN-γ responses to mitogen increased with age, confirming that this response is significantly affected by age, as previously reported in QFT-IT [ 27 ]. Consistent with previous research, higher IFN-γ responses to mitogen were observed in the first few years of life, then decreased during adult life, which is due to immune maturation and subsequent immunosenescence [ 28 ]. However, inverse relationship was found between antigens induced IFN-γ responses and age. A research from Tebruegge et al. confirmed our results that IFN-γ responses to antigen are significantly higher in children than in adults, indicating that the ability of T cells to generate MTB-specific IFN-γ responses was not negatively impacted by young age [ 28 ]. The median IFN-γ value in response to mitogen was higher in LTBI patients than in TB cases, suggesting that the potential ability of the immune system to respond to the antigenic stimuli was higher in children with LTBI. However, the magnitude of TB1 and TB2 responses had no significant difference between LTBI and TB cases, even in children grouped by age, indicating that the assay is not sutible to differentiate from those infection states. In conclusion, QFT-Plus assay is accurate in children and adolescents with active TB. IFN-γ responses to mitogen and MTB antigens are significantly affected by age. Furthermore, our data shows that the new antigen tube TB2 increases the assay sensitivity. Further head-to-head comparisons are needed to determine whether QFT-Plus assays perform better than QFT-GIT in children. Abbreviations EPTB extrapulmonary tuberculosis IFN-γ interferon gamma IGRAs Interferon gamma release assays LTBI latent tuberculosis infection MTB Mycobacterium tuberculosis PTB pulmonary tuberculosis QFT-IT QuantiFERON-TB Gold In Tube QFT-Plus QuantiFERON-TB Gold Plus TB tuberculosis TB1 antigen tube TB2 antigen tube Declarations Funding This work was supported by National Natural Science Foundation of China (82170007), Beijing Natural Science Foundation (7224328), and Funding for Reform and Development of Beijing Municipal Health Commission. Declaration of Competing Interests The authors declare that they have no competing interests. Ethical approval The study was approved by the Ethics Committee of Beijing Children’s Hospital, Capital Medical University ([2024]-Y-126-D). This study was conducted in accordance with the Declaration of Helsinki. Acknowledgments The authors gratefully acknowledge all participants and staff for their contribution to the study. Availability of data and materials The datasets used and/or analyzed during the current study available from the corresponding author on reasonable request. Author contributions LS and YC initiated and designed the study. YY, YG, YW, and JX conducted the experiment. HZ, YW, and FL analyzed the data. HZ, HQ, and WJ was responsible for writing the manuscript. All authors have read and approved the final manuscript. References World Health Organization. Global Tuberculosis Report 2023. Geneva, Switzerland: World Health Organization; 2023. Buonsenso D, Seddon JA, Esposito S, Barcellini L. QuantiFERON-TB Gold Plus Performance in Children: A Narrative Review. Pediatr Infect Dis J. 2023;42:e158–65. Churchyard GJ, Fielding KL, Grant AD. A trial of mass isoniazid preventive therapy for tuberculosis control. N Engl J Med. 2014;370:1662–3. Marais BJ, Gie RP, Schaaf HS, Hesseling AC, Obihara CC, Starke JJ, et al. 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Performance of QuantiFERON-TB Gold Plus assays in children and adolescents at risk of tuberculosis: a cross-sectional multicentre study. Thorax. 2022;77:1193–201. QIAGEN. Quantiferon-Tb gold plus (QFT-Plus) ELISA package insert. rev. Available: www.QuantiFERON.com [Accessed 25 Apr 2021]. Horne DJ, Jones BE, Kamada A, Fukushima K, Winthrop KL, Siegel SAR, et al. Multicenter study of QuantiFERON((R))-TB Gold Plus in patients with active tuberculosis. Int J Tuberc Lung Dis. 2018;22:617–21. Lombardi G, Petrucci R, Corsini I, Bacchi Reggiani ML, Visciotti F, Bernardi F et al. Quantitative Analysis of Gamma Interferon Release Assay Response in Children with Latent and Active Tuberculosis. J Clin Microbiol. 2018;56. Tebruegge M, de Graaf H, Sukhtankar P, Elkington P, Marshall B, Schuster H, et al. Extremes of age are associated with indeterminate QuantiFERON-TB gold assay results. J Clin Microbiol. 2014;52:2694–7. Additional Declarations No competing interests reported. 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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-5399017","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":376751258,"identity":"bea31e24-07fb-4605-bc9f-87ea4a15dd04","order_by":0,"name":"Huiwen Zheng","email":"","orcid":"","institution":"Beijing Children’s Hospital","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Huiwen","middleName":"","lastName":"Zheng","suffix":""},{"id":376751259,"identity":"3b5f204c-e2a9-48d2-b057-8ccf085fd440","order_by":1,"name":"Yanhong Yu","email":"","orcid":"","institution":"Shenyang chest hospital","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Yanhong","middleName":"","lastName":"Yu","suffix":""},{"id":376751260,"identity":"ddbf456c-7c6f-44ad-a745-36eb7682cfc7","order_by":2,"name":"Yonghong Wang","email":"","orcid":"","institution":"Beijing Children’s Hospital","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Yonghong","middleName":"","lastName":"Wang","suffix":""},{"id":376751261,"identity":"6175b034-48fd-4aae-bcac-0f015e8fd241","order_by":3,"name":"Yajie Guo","email":"","orcid":"","institution":"Beijing Children’s Hospital","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Yajie","middleName":"","lastName":"Guo","suffix":""},{"id":376751262,"identity":"241ec539-895c-4b40-9594-940920c7947d","order_by":4,"name":"Yang Wang","email":"","orcid":"","institution":"Beijing Children’s Hospital","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Yang","middleName":"","lastName":"Wang","suffix":""},{"id":376751263,"identity":"92093f5c-e3b9-4ea8-87fb-26991f0ec6fa","order_by":5,"name":"Feina Li","email":"","orcid":"","institution":"Beijing Children’s Hospital","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Feina","middleName":"","lastName":"Li","suffix":""},{"id":376751264,"identity":"dd1b0c3f-f4ab-4d6e-aabf-db385dc9f477","order_by":6,"name":"Jing Xiao","email":"","orcid":"","institution":"Beijing Children’s Hospital","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Jing","middleName":"","lastName":"Xiao","suffix":""},{"id":376751265,"identity":"6a3bc2a0-2c0d-43ba-b4e9-3b5ee173f7c0","order_by":7,"name":"Hui Qi","email":"","orcid":"","institution":"Beijing Children’s Hospital","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Hui","middleName":"","lastName":"Qi","suffix":""},{"id":376751266,"identity":"cbdc767d-6682-4fff-89c8-7d3b6ecf2393","order_by":8,"name":"Weiwei Jiao","email":"","orcid":"","institution":"Beijing Children’s Hospital","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Weiwei","middleName":"","lastName":"Jiao","suffix":""},{"id":376751272,"identity":"fb826c5e-b6fc-4f1c-8acc-3d431a628e7b","order_by":9,"name":"Yu Chen","email":"","orcid":"","institution":"Shenyang chest hospital","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Yu","middleName":"","lastName":"Chen","suffix":""},{"id":376751273,"identity":"c9aea9bc-70d1-4750-b787-5c71790e58c8","order_by":10,"name":"Lin Sun","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAvUlEQVRIiWNgGAWjYHACxgMJDAcYDNgbGx9+IFYPRAvP4WZjCaK1gJCBRHqbAA8xyuVn5B448HDHHXlzyYdtDBIMdnK6DQS0GNzISziQeOaZ4c7ZiW0PChiSjc0OENIikWNwILHtcILB7cR2AwmGA4nbCGmRnwHTcvNgmwQPMVoYbsC03GAkUovBmTcgLc8MN5xJBAayARF+kW/PMXz4s+2OvMHx4w8ffqiwkyOoBd1S0pSPglEwCkbBKMABAKPpS+DDz+gWAAAAAElFTkSuQmCC","orcid":"","institution":"Beijing Children’s Hospital","correspondingAuthor":true,"submittingAuthor":false,"prefix":"","firstName":"Lin","middleName":"","lastName":"Sun","suffix":""}],"badges":[],"createdAt":"2024-11-06 03:08:21","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5399017/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5399017/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":71144788,"identity":"f067d954-4a80-4528-b7ed-d8fb8fb904cd","added_by":"auto","created_at":"2024-12-11 14:15:06","extension":"jpeg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":345637,"visible":true,"origin":"","legend":"\u003cp\u003eFlow chart of the study population. QFT-Plus, QuantiFERON-TB Gold Plus; TB, tuberculosis; LTBI, latent tuberculosis infection; PTB: pulmonary tuberculosis; EPTB: extrapulmonary tuberculosis; POS, positive; NEG, negative, IND, indeterminate.\u003c/p\u003e","description":"","filename":"floatimage1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-5399017/v1/5147a89e8c6c70d5026ffb5f.jpeg"},{"id":71144787,"identity":"6cad1385-0fef-42de-bc89-998e015cc39d","added_by":"auto","created_at":"2024-12-11 14:15:06","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":97895,"visible":true,"origin":"","legend":"\u003cp\u003eIndividual nil-corrected IFN-γ levels in response to both TB antigens and mitogen in patients according to final diagnoses (mitogen (A), TB1 (B), and TB2 (C)) and disease localization (mitogen (D), TB1 (E), and TB2 (F)). Each point on the graph represents an individual result. Median values of IFN-γ production are indicated as red lines. The cutoff values for positive and indeterminate QFT-Plus are represented by red dotted lines at 0.35 and 0.50 IU/ml. QFT-Plus, QuantiFERON-TB Gold Plus; TB, tuberculosis; PTB: pulmonary tuberculosis; EPTB: extrapulmonary tuberculosis.\u003c/p\u003e","description":"","filename":"2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5399017/v1/090f1ee5a923764ba30a70ce.jpg"},{"id":71144789,"identity":"d7fae1a9-44a7-4614-8048-b25a43826913","added_by":"auto","created_at":"2024-12-11 14:15:06","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":53777,"visible":true,"origin":"","legend":"\u003cp\u003eIndividual nil-corrected IFN-γ levels in response to both TB antigens and mitogen in patients according to age (mitogen (A), TB1 (B), and TB2 (C)). Each point on the graph represents an individual result. Median values of IFN-γ production are indicated as red lines. The cutoff values for positive and indeterminate QFT-Plus are represented by red dotted lines at 0.35 and 0.50 IU/ml. \u003csup\u003e*\u003c/sup\u003e\u003cem\u003eP\u003c/em\u003e \u0026lt; 0.05, \u003csup\u003e**\u003c/sup\u003e\u003cem\u003eP\u003c/em\u003e \u0026lt; 0.01,\u003csup\u003e ***\u003c/sup\u003e\u003cem\u003eP\u003c/em\u003e \u0026lt; 0.001. QFT-Plus, QuantiFERON-TB Gold Plus.\u003c/p\u003e","description":"","filename":"3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5399017/v1/bfb907c0f1bd58355df1b880.jpg"},{"id":71144790,"identity":"4b2a2c0d-b1d7-40bd-a336-dd775335ee04","added_by":"auto","created_at":"2024-12-11 14:15:06","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":62278,"visible":true,"origin":"","legend":"\u003cp\u003eCorrelation between IFN-γ concentrations and age. Individual Nil-corrected IFN-γ levels in response to A) mitogen, B) TB1 antigen and C) TB2 antigen in the whole study population.The cut-off values for positive and indeterminate QFT-Plus are represented by dotted red lines at 0.35 and 0.50 IU/ml, respectively. The bold lines indicate the linear regressions. The values shown are Pearson’s correlation coefficients (r) and their corresponding \u003cem\u003eP\u003c/em\u003e value.\u003c/p\u003e","description":"","filename":"4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5399017/v1/23d7bc4d53f3668ed29899d5.jpg"},{"id":71145877,"identity":"d2499a16-aa39-4a06-b8f2-62adfb284feb","added_by":"auto","created_at":"2024-12-11 14:23:06","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":64342,"visible":true,"origin":"","legend":"\u003cp\u003eIndividual nil-corrected IFN-γ levels in response to both TB antigens and mitogen in patients with active TB and LTBI (A). Individual IFN-γ levels in response to nil-corrected TB1 (B) and TB2 antigen (C) in active TB and LTBI patients according age groups. Median values of IFN-γ production are indicated as red lines. The cut-off values for positive and indeterminate QFT-Plus are represented by dotted red and green lines at 0.35 and 0.50 IU/ml, respectively.\u003c/p\u003e","description":"","filename":"5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5399017/v1/47f0de6ad0a36a511027d566.jpg"},{"id":71145886,"identity":"ec54992f-d060-44f9-8508-09153b743d1f","added_by":"auto","created_at":"2024-12-11 14:23:11","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1292443,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5399017/v1/e50c53e6-7ac8-424e-ae65-24c79e5edbc9.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Analysis of QuantiFERON-TB Gold Plus assay in Children and Adolescents with Latent and Active Tuberculosis in China","fulltext":[{"header":"Introduction","content":"\u003cp\u003eTuberculosis (TB), caused by \u003cem\u003eMycobacterium tuberculosis\u003c/em\u003e (MTB), is one of the leading causes of death worldwide, with approximately 10.6\u0026nbsp;million incident cases in 2022 [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Pediatric TB accounted for 12% of the total cases, bearing a substantial part of the TB epidemic [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Almost one-quarter of the world\u0026rsquo;s population is latently infected with MTB, and the risk of progression to TB disease is much higher in infants (30%-40%) and children (10%-20%) than in adults within the first 2 years after infection, constituting a large reservoir that sustains TB disease [\u003cspan additionalcitationids=\"CR3\" citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Therefore, early detection and initiation preventive therapy for MTB infection are key strategies in controlling pediatric TB. Moreover, due to the nonspecific clinical presentation, paucibacillary nature of TB, extrapulmonary localization and difficulties in obtaining sputum samples, the diagnosis of pediatric TB is hampered [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Current guidelines recommend a combination of clinical, microbiological, radiological, and immunological approaches to improve the diagnosis of pediatric TB [\u003cspan additionalcitationids=\"CR8\" citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eInterferon gamma release assays (IGRAs) are immunoassays based on the in vitro detection of interferon gamma (IFN-γ) produced by specifically sensitized T cells, following stimulation with MTB specific antigens, which contributes to identify individuals infected with MTB, and aid to diagnosis of pediatric TB disease [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. Recently, the 4th-generation QuantiFERON-TB Gold Plus (QFT-Plus) (QIAGEN, Germantown, Maryland, USA) IGRA has been introduced. Different from its predecessor QuantiFERON-TB Gold In Tube (QFT-IT), QFT-Plus has no TB7.7 peptides in its antigenic components, namely first antigen tube (TB1) directed at CD4\u0026thinsp;+\u0026thinsp;T cells, but added a second antigen tube (TB2) containing additional shorter ESAT-6 and CFP-10 peptides to elicit both CD4\u0026thinsp;+\u0026thinsp;and CD8\u0026thinsp;+\u0026thinsp;T cell responses, hoping to improve the sensitivity for the detection of MTB infection [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. As there are no data about QFT-Plus performance in children and adolescents with active TB and latent tuberculosis infection (LTBI) in China, we performed this study to evaluate the accuracy of QFT-Plus assay, and analyze the quantitative IFN-γ responses to TB antigens and mitogen according to age, disease diagnosis and anatomic sites, which will provide the basis for clinical diagnosis and treatment.\u003c/p\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStudy design\u003c/h2\u003e \u003cp\u003eThis was a retrospective study for patients \u0026lt;25 years old with suspected active TB (symptomatic patients) and otherwise screened for LTBI, received QFT-Plus tests at Beijing Children\u0026rsquo;s Hospital and Shenyang Chest Hospital from August 2022 to March 2024. Demographic and clinical data were extracted from their electronic medical record, including age, sex, QFT-Plus results, microbiologic findings and final diagnosis.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003ePatient categories\u003c/h3\u003e\n\u003cp\u003eThe diagnosis of TB disease is based on epidemiologic, clinical, radiologic, and microbiologic findings [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. According to the composite reference standard, patients with TB disease were categorized into (1) bacteriologically confirmed TB: positive results of smear microscopy or culture or molecular tests; (2) clinically diagnosed TB: at least 1 symptom and sign, X-ray abnormalities suggestive of tuberculosis, and at least 1 of the following: clinical and radiologic improvement after anti-TB treatment, exposure history of active TB, positive results of tuberculin skin test, or interferon-γ release assay.\u003c/p\u003e \u003cp\u003eBased on the anatomic site, the patients with TB disease were categorized into (1) pulmonary tuberculosis (PTB): any bacteriologically confirmed or clinically diagnosed case of TB involving the lung parenchyma or the tracheobronchial tree, and miliary TB is classified as PTB (2) extrapulmonary tuberculosis (EPTB): any bacteriologically confirmed or clinically diagnosed case of TB involving organs other than the lungs (e.g. pleura, peripheral lymph nodes, abdomen, genitourinary tract, skin, joints and bones, meninges) [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. (3) Combined tuberculosis: concurrent pulmonary and extrapulmonary TB.\u003csup\u003e14\u003c/sup\u003e Diagnosis of LTBI was based on positive QFT-Plus and absence of any clinical, microbiological, and radiological features that would suggest active disease [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. non-TB: cases with other diagnosis.\u003c/p\u003e\n\u003ch3\u003eQFT-Plus assay\u003c/h3\u003e\n\u003cp\u003eAccording to the manufacturer's instructions, 1 ml of venipuncture blood collected in lithium heparin tubes was transferred into each of the four separate test tubes: a negative control (nil) tube, a positive control (mitogen) tube and two antigen tubes (TB1 and TB2). Each tube was incubated for 16 to 24 h at 37\u0026deg;C, followed by centrifugation for 15 min at 2,000 xg to collect supernatants and assess IFN-γ levels (IU/ml) by enzyme-linked immunosorbent assay. The results were considered positive if either the IFN-γ values of TB1-Nil or TB2-Nil were \u0026ge;\u0026thinsp;0.35 IU/mL and \u0026ge;\u0026thinsp;25% of the Nil value. Results showing a nil value of \u0026gt;8.0 IU/ml or a mitogen value of \u0026lt;0.5 IU/ml were considered indeterminate.\u003c/p\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003eStatistical analysis\u003c/h2\u003e \u003cp\u003eCategorical variables are reported as absolute frequencies and percentages. Sensitivity was calculated based on the proportion of positive QFT-Plus results with 95% CI, indeterminate results were excluded from this particular analysis. Quantitative background-corrected antigen-stimulated IFN-γ responses in QFT-Plus assay among subgroups were compared with Kruskal-Wallis tests. Total agreement and Cohen\u0026rsquo;s kappa coefficient (k) were used to quantify concordance between TB1 and TB2 results. Statistical analysis was performed using GraphPad Prism v8.0.1 (GraphPad, San Diego, CA, USA), with statistical significance defined as a \u003cem\u003eP\u003c/em\u003e value of \u0026lt;0.05.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eStudy population\u003c/h2\u003e \u003cp\u003eA total of 18482 patients were recruited, including 179 (1.0%) patients with active TB disease, 334 (1.8%) LTBI and 17969 (97.2%) non-TB disease (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Of all the patients tested by QFT-Plus assay, 491 (2.7%) were positive, 16915 (91.5%) were negative, and 1076 (5.8%) had indeterminate results. Of the 513 patients with TB disease and LTBI, there were 125 (24.4%, 125/513) adolescents (\u0026ge;\u0026thinsp;18 years of age) and 388 (75.6%, 388/513) children (\u0026lt;18 years of age), including 11/388 (2.8%) aged \u0026lt;1 year, 72/388 (18.6%) aged 1 to 5 years, 109/388 (28.1%) aged 6 to 10 years, and 196/388 (50.5%) aged 11 to 17 years. Of the 179 active TB cases, 86 (48.0%, 86/179) cases were bacteriologically confirmed TB and 93 (52.0%, 93/179) cases were clinically confirmed TB. Besides, 108 (60.3%, 108/179) PTB, 38 (21.2%, 38/179) EPTB and 33 (18.4%, 33/179) combined TB were confirmed according to anatomic sites (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eStudy population with TB disease and LTBI\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eParameter\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eTotal no. (%) (n\u0026thinsp;=\u0026thinsp;513)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNo. bacteriologically confirmed TB (%) (n\u0026thinsp;=\u0026thinsp;86)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eNo. clinically confirmed TB (%) (n\u0026thinsp;=\u0026thinsp;93)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eNo. LTBI (%) (n\u0026thinsp;=\u0026thinsp;334)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGender\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMale\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e263 (51.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e45 (52.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e56 (60.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e162 (48.5)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFemale\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e250 (48.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e41 (47.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e37 (39.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e172 (51.5)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"4\" nameend=\"c5\" namest=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u0026lt;1 year\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e11 (2.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7 (8.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2 (2.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2 (0.6)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1\u0026ndash;5 years\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e72 (14.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8 (9.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e13 (14.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e51 (15.3)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e6\u0026ndash;10 years\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e109 (21.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e11 (12.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e19 (20.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e79 (23.7)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e11\u0026ndash;17 years\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e196 (38.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e14 (16.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e29 (31.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e153 (45.8)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e18\u0026ndash;24 years\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e125 (24.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e46 (53.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e30 (32.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e49 (14.7)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePatient group\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePTB only\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e108 (21.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e55 (64.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e53 (57.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eEPTB only\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e38 (7.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e12 (14.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e26 (28.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCombined TB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e33 (6.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e19 (22.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e14 (15.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eAccuracy of QFT-Plus and agreement between TB1 and TB2\u003c/h3\u003e\n\u003cp\u003eAmong the 179 active TB patients tested by QFT-Plus assay, 146 (81.6%) were positive, 29 (19.9%) were negative, and 4 (2.2%) scored indeterminate results (insufficient mitogen response). As shown in Table \u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, the overall sensitivity for active TB was 83.4% (77.9%-89.0%), and specificity was 98.0% (97.8%-98.2%). Except for the subgroup of patients with combined TB (71.9% [55.4%-88.3%]) and patients\u0026thinsp;\u0026lt;\u0026thinsp;1 year of age (57.1% [7.7%-106.6%]), the assay sensitivity was \u0026gt;78% among all subgroups analyzed, but no significant difference was observed among age groups. Among subgroup with final diagnoses of active TB, QFT-Plus showed higher sensitivity in clinically confirmed TB patients than in bacteriologically confirmed TB patients (87.8% vs 78.8%), but this was not statistically significant. Similar sensitivity of QFT-Plus was observed in the subgroup of patients with PTB and EPTB, but higher than that and in subgroups of combined TB (86.0% vs 86.1% vs 71.9%).\u003c/p\u003e \u003cp\u003eAfter excluding the indeterminate results, 175 active TB cases with QFT-Plus results were available (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). 131 cases were identified by both TB1 and TB2, 5 identified by TB1 only and 12 identified by TB2 only, with percent agreement between TB1 and TB2 was 90.3% and a Cohen\u0026rsquo;s Kappa efficient of 0.700. Moderate agreement between TB1 and TB2 was observed among EPTB (κ\u0026thinsp;=\u0026thinsp;0.583) and clinically confirmed TB group (κ\u0026thinsp;=\u0026thinsp;0.585). The agreement was substantial among PTB (κ\u0026thinsp;=\u0026thinsp;0.706) and combined TB (κ\u0026thinsp;=\u0026thinsp;0.776), and almost perfect among bacteriologically confirmed TB (κ\u0026thinsp;=\u0026thinsp;0.820) cases.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eSensitivity of QFT plus assay in patients with active TB\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ePatient group\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eNo. of patients\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c5\" namest=\"c3\"\u003e \u003cp\u003eNo. (%) QFT-Plus\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eSensitivity\u003c/p\u003e \u003cp\u003e(95% CI) (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u003cem\u003eP\u003c/em\u003e value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003ePositive\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eNegative\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eIndeterminate\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAll active TB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e179\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e146 (81.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e29 (19.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e4 (2.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e83.4 (77.9\u0026ndash;89.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eComposite reference standard\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.111\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBacteriologically confirmed TB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e86\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e67 (77.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e18 (20.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1 (1.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e78.8 (70.0-87.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eClinically confirmed TB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e93\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e79 (84.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e11 (11.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3 (3.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e87.8 (80.9\u0026ndash;94.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAnatomic site\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.151\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePTB only\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e108\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e92 (85.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e15 (13.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1 (0.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e86.0 (79.3\u0026ndash;92.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eEPTB only\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e38\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e31 (81.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e5 (13.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2 (5.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e86.1 (74.2\u0026ndash;98.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCombined TB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e33\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e23 (69.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e9 (27.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1 (3.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e71.9 (55.4\u0026ndash;88.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.255\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u0026lt;1 year\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e4 (44.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e3 (33.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2 (22.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e57.1 (7.7-106.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1\u0026ndash;5 years\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e21\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e16 (76.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e3 (14.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2 (9.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e84.2 (66.2-102.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e6\u0026ndash;10 years\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e25 (83.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e5 (16.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0 (0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e83.3 (69.2\u0026ndash;97.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e11\u0026ndash;17 years\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e43\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e34 (79.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e9 (20.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0 (0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e79.0 (66.4\u0026ndash;91.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e18\u0026ndash;24 years\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e76\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e67 (88.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e9 (11.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0 (0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e88.2 (80.7\u0026ndash;95.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGender\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.905\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMale\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e101\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e81 (80.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e17 (16.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3 (3.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e80.2 (72.3\u0026ndash;88.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFemale\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e78\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e65 (83.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e13 (16.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1 (1.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e83.3 (73.7\u0026ndash;90.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eTest agreement between TB1 and TB2 in children with active TB\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"12\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c11\" colnum=\"11\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c12\" colnum=\"12\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eCategory\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eTotal no.\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003eMean\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colspan=\"5\" nameend=\"c10\" namest=\"c6\"\u003e \u003cp\u003eNo. with TB1/TB2 results\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c11\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ePercent agreement\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c12\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eKappa value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eTB1\u003c/p\u003e \u003cp\u003e(IU/ml)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eTB2\u003c/p\u003e \u003cp\u003e(IU/ml)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e \u003cp\u003e+/-\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003e+/+\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003e-/+\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c10\"\u003e \u003cp\u003e-/-\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eATB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e175\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3.45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e131\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e90.3%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e0.700\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePTB only\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e107\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3.22\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3.63\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e84\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e91.6%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e0.706\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eEPTB only\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e36\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2.45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3.23\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e26\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e86.1%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e0.583\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCombined TB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e32\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2.90\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3.12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e21\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e90.6%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e0.776\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBacteriologically confirmed TB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e85\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2.82\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3.45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e65\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e94.1%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e0.820\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eClinically confirmed TB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e90\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3.29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3.56\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e66\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e86.7%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e0.585\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e\n\u003ch3\u003eQuantitative QFT-Plus responses to TB antigens and mitogen according to diagnosis\u003c/h3\u003e\n\u003cp\u003eIFN-γ levels in response to mitogen and nil-corrected TB antigens in different diagnostic groups are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. Regarding disease localization, median IFN-γ responses to mitogen were lower in cases of EPTB (7.79 IU/ml) than in cases of PTB (8.58 IU/ml) and combined TB (8.36 IU/ml), although the difference was not statistically significant. Though the TB2 levels in the QFT-Plus antigen tubes were higher than the TB1 levels in children with active TB (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e), no significant differences in IFN-γ production in response to TB1 and TB2 antigens were observed among subgroup with final diagnoses (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.57 for TB1, \u003cem\u003eP\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.17 for TB2, respectively) and subgroup of patients with disease localization (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.54 for TB1, \u003cem\u003eP\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.76 for TB2, respectively).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eQuantitative QFT-Plus responses to TB antigens and mitogen according to age\u003c/h2\u003e \u003cp\u003eAs shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, IFN-γ production in response to mitogen observed among children \u0026lt;1 year of age (median of 5.72 IU IFN-γ/ml) was significantly lower than that among children 6 to 10 years of age (median of 8.96 IU IFN-γ/ml, \u003cem\u003eP\u003c/em\u003e\u0026lt;0.01), 11 to 17 years of age (median of 9.32 IU IFN-γ/ml, \u003cem\u003eP\u003c/em\u003e\u0026lt;0.001), and youth 18 to 25 years (median of 9.03 IU IFN-γ/ml, \u003cem\u003eP\u003c/em\u003e\u0026lt;0.01). Besides, children aged 1 to 5 years had significantly lower IFN-γ response to mitogen (median of 8.00 IU IFN-γ/ml) than that in children 11 to 17 years of age (median of 9.32 IU IFN-γ/ml, \u003cem\u003eP\u003c/em\u003e\u0026lt;0.05). The median IFN-γ responses to TB1 antigen was significantly lower in children \u0026lt;1 year of age (median of 1.38 IU IFN-γ/ml) than in children 1 to 5 years of age (median of 3.95 IU IFN-γ/ml, \u003cem\u003eP\u003c/em\u003e\u0026lt;0.05). And significant difference in IFN-γ production in response to TB2 antigen was observed among age subgroups (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.04).\u003c/p\u003e \u003cp\u003eLinear regression analysis showed that there was significant positive correlation between age and IFN-γ responses to mitogen (Pearson\u0026rsquo;s correlation coefficient \u003cem\u003er\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.1660 [95% CI, 0.08054 to 0.2490]; \u003cem\u003eP\u003c/em\u003e\u0026lt;0.01), but negative correlation between age and IFN-γ responses to TB1 (Pearson\u0026rsquo;s \u003cem\u003er\u003c/em\u003e =-0.1030 [95% CI, -0.1879 to -0.01662]; \u003cem\u003eP\u003c/em\u003e\u0026lt;0.05) and TB2 antigen (Pearson\u0026rsquo;s \u003cem\u003er\u003c/em\u003e =-0.08818 [95% CI, -0.1734 to -0.001625]; \u003cem\u003eP\u003c/em\u003e\u0026lt;0.05) (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003eQuantitative values of TB Ag to discriminate active TB from LTBI\u003c/h2\u003e \u003cp\u003eThe median mitogen response value for LTBI (9.20 IU/ml) was higher with respect to TB cases (8.37 IU/ml), but there was no significant difference (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). The mean values of TB1 and TB2 antigens in active TB (TB1: 3.44 IU/ml; TB2: 3.81 IU/ml) were higher than those in LTBI cases (TB1: 3.32 IU/ml; TB2: 3.44 IU/ml), respectively, but the difference was not statistically significant (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Besides, there was no significant difference in response to QFT-Plus TB antigens in active TB and LTBI cases according to age groups (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eThis study is preliminary to evaluate the performance of QFT-Plus in children and adolescents in China. We found that 5.8% (1076/18482) patients evaluated with QFT-Plus had indeterminate results, which is smaller than what has been reported from our previous studies on QFT-IT in children [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. A recent multicenter study by Buonsenso et al. revealed an overall rate of indeterminate QFT-Plus results of 3.1% (11 of 358 children) [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e], and their another research reported 2.5% (5/198) children evaluated with QFT-Plus had an indeterminate result [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. And Nguyen et al. found that only 1/222 (0.45%) children had indeterminate QFT-Plus results in Vietnam [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e], confirming that QFT-Plus is effective in children. Among the 4 cases (\u0026le;\u0026thinsp;3 years) with indeterminate results in patients with active TB, one had congenital immunodeficiency, one had bacterial infections, and 2 had miliary and/or central nervous system (CNS) TB, suggesting that young age, CNS disease, and ongoing infection may be a stronger driver of indeterminate test results [\u003cspan additionalcitationids=\"CR20\" citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eTo our knowledge, little studies have evaluated the performance of QFT-Plus in children with TB disease so far. Our data showed the overall sensitivity and specificity was 83.4% and 98.0%, respectively, comparebale to most studies. The currently largest multicenter study conducted in Europe reported the overall sensitivity and specificity of QFT-Plus was 83.8% and 90.1% in 358 children with active TB, respectivley [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e], and another study from the same group found a sensitivity of 83.3% in 12 children received a final diagnosis of active TB [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. Another larger muticenter study with 158 pediatric TB disease conducted in Spain, realved a sensitivity of the assay was 82.9% [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e], another two studies from the same group reported the sensitivity of 87.3% in 102 paediatric TB cases [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e], and 83.6% in 189 pediatric TB disease [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. However, one study in Vietnam reported the sensitivity of the assay was only 54% in 33 children with confirmed TB disease, while 84.2% in patients with isolated PTB (n\u0026thinsp;=\u0026thinsp;19), and 14.3% in patients with EPTB (n\u0026thinsp;=\u0026thinsp;7) and concomitant PTB and EPTB, respectively (n\u0026thinsp;=\u0026thinsp;7) [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. The sensitivity in PTB is comparable with our founding of 86.0%, indicating QFT-Plus had a rather good sensitivity in patients with exclusive PTB. The difference in sensitivity of QFT-Plus on EPTB may be depend on the extra-pulmonary TB site, which performs worse in patients with miliary and/or CNS TB, as well as in immunocompromised children [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e].\u003csup\u003e17\u003c/sup\u003e So as has been claimed, QFT-Plus assays has not enhanced sensitivity than previous generation IGRAs [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eSubgroup analyses demonstrated that the sensitivity of QFT-Plus was higher in clinically confirmed TB than that in bacteriologically confirmed TB cases, which was consistent with a muticenter study in Spain [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e], but none were statistically significant. Howerver, another study by the same group showed the opposite results [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. So whether there was a relationship between antigenic load and the magnitude of IFN-γ responses, need further to be confirmed by larger size of these subgroups. We found the TB1/TB2 agreement was 90.3%, lower than that reported in Vietnam (96.4%) [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. According to previous research [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e], the TB2 levels in the QFT-Plus antigen tubes were higher than the TB1 levels. And 6.9% (12/175) patients with negative responses in the TB1 tube were identified by TB2 tube, indicating that TB2 stimulation induces a CD8 T-cell response that are in addition to CD4-response.\u003c/p\u003e \u003cp\u003eThe analyses of quantitative mitogen and antigen-induced IFN-γ responses were lower in children\u0026thinsp;\u0026lt;\u0026thinsp;1 year of age, a group at higher risk of indeterminate assay results, suggesting that they are unable to produce a response to ensure a valid QFT-Plus result. Linear regression analysis demonstrated that IFN-γ responses to mitogen increased with age, confirming that this response is significantly affected by age, as previously reported in QFT-IT [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. Consistent with previous research, higher IFN-γ responses to mitogen were observed in the first few years of life, then decreased during adult life, which is due to immune maturation and subsequent immunosenescence [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. However, inverse relationship was found between antigens induced IFN-γ responses and age. A research from Tebruegge et al. confirmed our results that IFN-γ responses to antigen are significantly higher in children than in adults, indicating that the ability of T cells to generate MTB-specific IFN-γ responses was not negatively impacted by young age [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. The median IFN-γ value in response to mitogen was higher in LTBI patients than in TB cases, suggesting that the potential ability of the immune system to respond to the antigenic stimuli was higher in children with LTBI. However, the magnitude of TB1 and TB2 responses had no significant difference between LTBI and TB cases, even in children grouped by age, indicating that the assay is not sutible to differentiate from those infection states.\u003c/p\u003e \u003cp\u003eIn conclusion, QFT-Plus assay is accurate in children and adolescents with active TB. IFN-γ responses to mitogen and MTB antigens are significantly affected by age. Furthermore, our data shows that the new antigen tube TB2 increases the assay sensitivity. Further head-to-head comparisons are needed to determine whether QFT-Plus assays perform better than QFT-GIT in children.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cdiv class=\"DefinitionList\"\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eEPTB\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eextrapulmonary tuberculosis\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eIFN-γ\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003einterferon gamma\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eIGRAs\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eInterferon gamma release assays\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eLTBI\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003elatent tuberculosis infection\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eMTB\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003e \u003cem\u003eMycobacterium tuberculosis\u003c/em\u003e \u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003ePTB\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003epulmonary tuberculosis\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eQFT-IT\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eQuantiFERON-TB Gold In Tube\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eQFT-Plus\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eQuantiFERON-TB Gold Plus\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eTB\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003etuberculosis\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eTB1\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eantigen tube\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eTB2\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eantigen tube\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported by National Natural Science Foundation of China (82170007),\u0026nbsp;Beijing Natural Science Foundation (7224328),\u0026nbsp;and Funding for Reform and Development of Beijing Municipal Health Commission.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDeclaration of Competing Interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthical approval\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe study was approved by the Ethics Committee of Beijing Children\u0026rsquo;s Hospital, Capital Medical University ([2024]-Y-126-D).\u0026nbsp;This study was conducted in accordance with the Declaration of Helsinki.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors gratefully acknowledge all participants and staff for their contribution to the study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets used and/or analyzed during the current study available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eLS and YC initiated and designed the study. YY, YG, YW, and JX conducted the experiment. HZ, YW, and FL analyzed the data. HZ, HQ, and WJ was responsible for writing the manuscript. All authors have read and approved the final manuscript.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eWorld Health Organization. Global Tuberculosis Report 2023. Geneva, Switzerland: World Health Organization; 2023.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBuonsenso D, Seddon JA, Esposito S, Barcellini L. QuantiFERON-TB Gold Plus Performance in Children: A Narrative Review. Pediatr Infect Dis J. 2023;42:e158\u0026ndash;65.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChurchyard GJ, Fielding KL, Grant AD. A trial of mass isoniazid preventive therapy for tuberculosis control. N Engl J Med. 2014;370:1662\u0026ndash;3.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMarais BJ, Gie RP, Schaaf HS, Hesseling AC, Obihara CC, Starke JJ, et al. The natural history of childhood intra-thoracic tuberculosis: a critical review of literature from the pre-chemotherapy era. Int J Tuberc Lung Dis. 2004;8:392\u0026ndash;402.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMandal N, Anand PK, Gautam S, Das S, Hussain T. Diagnosis and treatment of paediatric tuberculosis: An insight review. Crit Rev Microbiol. 2017;43:466\u0026ndash;80.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNewton SM, Brent AJ, Anderson S, Whittaker E, Kampmann B. Paediatric tuberculosis. Lancet Infect Dis. 2008;8:498\u0026ndash;510.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWorld Health Organization. 2014. Guidance for national tuberculosis programmes on the management of tuberculosis in children, 2nd ed.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBerti E, Galli L, Venturini E, de Martini M, Chiappini E. Tuberculosis in childhood: a systematic review of national and international guidelines. BMC Infect Dis. 2014;14(Suppl 1):S3.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKumar MK, Kumar P, Singh A. Recent advances in the diagnosis and treatment of childhood tuberculosis. J Nat Sci Biol Med. 2015;6:314\u0026ndash;20.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePai M, Kalantri S, Dheda K. New tools and emerging technologies for the diagnosis of tuberculosis: part II. Active tuberculosis and drug resistance. Expert Rev Mol Diagn. 2006;6:423\u0026ndash;32.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBarcellini L, Borroni E, Brown J, Brunetti E, Campisi D, Castellotti PF, et al. First evaluation of QuantiFERON-TB Gold Plus performance in contact screening. Eur Respir J. 2016;48:1411\u0026ndash;9.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eShafeque A, Bigio J, Hogan CA, Pai M, Banaei N. Fourth-Generation QuantiFERON-TB Gold Plus: What Is the Evidence? J Clin Microbiol. 2020;58.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGraham SM, Ahmed T, Amanullah F, Browning R, Cardenas V, Casenghi M, et al. Evaluation of tuberculosis diagnostics in children: 1. Proposed clinical case definitions for classification of intrathoracic tuberculosis disease. Consensus from an expert panel. J Infect Dis. 2012;205(Suppl 2):S199\u0026ndash;208.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWHO Operational Handbook on Tuberculosis. Module 5: Management of Tuberculosis in Children and Adolescents. Geneva: World Health Organization; 2022.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBuonsenso D, Delogu G, Perricone C, Grossi R, Careddu A, Maio DF et al. Accuracy of QuantiFERON-TB Gold Plus Test for Diagnosis of Mycobacterium tuberculosis Infection in Children. J Clin Microbiol. 2020;58.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZheng HW, Xiao J, Li FN, Chen H, Li DZ, Wang YH, et al. Interferon-gamma release assay for screening of tuberculosis infection in children. BMC Infect Dis. 2023;23:873.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBuonsenso D, Noguera-Julian A, Moroni R, Hernandez-Bartolome A, Fritschi N, Lancella L, et al. Performance of QuantiFERON-TB Gold Plus assays in paediatric tuberculosis: a multicentre PTBNET study. Thorax. 2023;78:288\u0026ndash;96.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNguyen DT, Phan H, Trinh T, Nguyen H, Doan H, Pham N, et al. Sensitivity and characteristics associated with positive QuantiFERON-TB Gold-Plus assay in children with confirmed tuberculosis. PLoS ONE. 2019;14:e0213304.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCritselis E, Amanatidou V, Syridou G, Spyridis NP, Mavrikou M, Papadopoulos NG, et al. The effect of age on whole blood interferon-gamma release assay response among children investigated for latent tuberculosis infection. J Pediatr. 2012;161:632\u0026ndash;8.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKay AW, Islam SM, Wendorf K, Westenhouse J, Barry PM. Interferon-gamma Release Assay Performance for Tuberculosis in Childhood. Pediatrics. 2018;141.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSali M, Buonsenso D, Goletti D, D'Alfonso P, Zumbo A, Fadda G, et al. Accuracy of QuantiFERON-TB Gold Test for Tuberculosis Diagnosis in Children. PLoS ONE. 2015;10:e0138952.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSoler-Garcia A, Gamell A, Santiago B, Monsonis M, Calvo C, Cobo E, et al. Diagnostic Accuracy of QuantiFERON-TB Gold Plus Assays in Children and Adolescents with Tuberculosis Disease. J Pediatr. 2020;223:212\u0026ndash;e51.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSoler-Garcia A, Gamell A, Santiago B, Monsonis M, Cobo-Vazquez E, Bustillo-Alonso M, et al. QuantiFERON-TB Gold Plus Assay Specificity in Children and Adolescents With Suspected Tuberculosis-A Multicenter Cross-sectional Study in Spain. Pediatr Infect Dis J. 2021;40:e348\u0026ndash;51.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSoler-Garcia A, Gamell A, Perez-Porcuna T, Soriano-Arandes A, Santiago B, Tortola T, et al. Performance of QuantiFERON-TB Gold Plus assays in children and adolescents at risk of tuberculosis: a cross-sectional multicentre study. Thorax. 2022;77:1193\u0026ndash;201.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eQIAGEN. Quantiferon-Tb gold plus (QFT-Plus) ELISA package insert. rev. Available: www.QuantiFERON.com [Accessed 25 Apr 2021].\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHorne DJ, Jones BE, Kamada A, Fukushima K, Winthrop KL, Siegel SAR, et al. Multicenter study of QuantiFERON((R))-TB Gold Plus in patients with active tuberculosis. Int J Tuberc Lung Dis. 2018;22:617\u0026ndash;21.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLombardi G, Petrucci R, Corsini I, Bacchi Reggiani ML, Visciotti F, Bernardi F et al. Quantitative Analysis of Gamma Interferon Release Assay Response in Children with Latent and Active Tuberculosis. J Clin Microbiol. 2018;56.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTebruegge M, de Graaf H, Sukhtankar P, Elkington P, Marshall B, Schuster H, et al. Extremes of age are associated with indeterminate QuantiFERON-TB gold assay results. J Clin Microbiol. 2014;52:2694\u0026ndash;7.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"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":"bmc-pediatrics","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bped","sideBox":"Learn more about [BMC Pediatrics](http://bmcpediatr.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/bped/default.aspx","title":"BMC Pediatrics","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Tuberculosis, Children, Interferon gamma release assay, QuantiFERON Plus","lastPublishedDoi":"10.21203/rs.3.rs-5399017/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5399017/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eObjective\u003c/h2\u003e \u003cp\u003eTo evaluate the accuracy of QuantiFERON-TB Gold Plus (QFT-Plus) assay, and analyze the quantitative interferon gamma (IFN-γ) responses to tuberculosis (TB) antigens and mitogen in children and adolescents with active TB and latent tuberculosis infection (LTBI) in China.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eA retrospective study was conducted among patients \u0026lt;25 years old with suspected active TB or screened for LTBI. All patients underwent QFT-Plus tests at Beijing Children\u0026rsquo;s Hospital and Shenyang Chest Hospital from August 2022 to March 2024. Demographic and clinical data were extracted from their electronic medical record.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eA total of 18482 patients were recruited, including 179 (1.0%) patients with active TB disease, 334 (1.8%) LTBI and 17969 (97.2%) non-TB disease. The 5.8% (176/18482) patients had indeterminate results. The overall sensitivity for active TB was 83.4%, and specificity was 98.0%. The percent agreement between TB1 and TB2 was 90.3%. The IFN-γ production in response to mitogen and TB antigens observed among children \u0026lt;1 year of age was lower than that among other age groups. There was significant positive correlation between age and IFN-γ responses to mitogen, but negative correlation between age and IFN-γ responses to TB1 and TB2 antigen. Besides, there was no significant difference in response to QFT-Plus TB antigens in active TB and LTBI cases.\u003c/p\u003e\u003ch2\u003eConclusion\u003c/h2\u003e \u003cp\u003eQFT-Plus assay is accurate in children and adolescents with active TB. IFN-γ responses to mitogen and MTB antigens are significantly affected by age. The new antigen tube TB2 increases the assay sensitivity.\u003c/p\u003e","manuscriptTitle":"Analysis of QuantiFERON-TB Gold Plus assay in Children and Adolescents with Latent and Active Tuberculosis in China","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-12-11 14:15:01","doi":"10.21203/rs.3.rs-5399017/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2024-11-11T15:42:58+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-11-08T14:25:15+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-11-08T14:23:40+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Pediatrics","date":"2024-11-06T03:05:35+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-pediatrics","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bped","sideBox":"Learn more about [BMC Pediatrics](http://bmcpediatr.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/bped/default.aspx","title":"BMC Pediatrics","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"d4d4334c-6852-4660-bf34-290873d560c7","owner":[],"postedDate":"December 11th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-06-04T03:08:20+00:00","versionOfRecord":[],"versionCreatedAt":"2024-12-11 14:15:01","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-5399017","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5399017","identity":"rs-5399017","version":["v1"]},"buildId":"7rjqhiLT3MXkJMwkYKINL","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}