The prevalence and development of anemia in community- acquired pneumonia patients and its association with the duration of hospitalization and mortality

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In critically ill hospitalized patients, mortality rates range from 5% to as high as 30–50%. There is an increasing interest in studying the anemia prevalence among hospitalized patients and its consequences in comorbidity and mortality. Considering that CAP is the second leading cause of hospital admission, this study investigates the prevalence and progression of anemia in CAP patients, and its association with hospital stay, mortality, and pneumonia severity. Methods This prospective observational study analyzed 60 patients admitted to the hospital with CAP, classified according to the pneumonia severity index (PSI). Hemoglobin levels were measured on the day of admission, the fourth day, the seventh day, and at discharge. Anemia was categorized into five categories: no anemia, mild anemia (Hgb 12-10g/dl), moderate (Hgb 10-8g/dl), severe (Hgb 7.9-6.5g/dl), and life threatening (Hgb < 6.5 g/dl). We examined the relationship between anemia and hospital stay duration, pneumonia severity, incidence of complication, mortality, and gender. Results Anemia was prevalent in 86.7% of patients hospitalized with CAP. Although our data did not show new development of anemia during hospitalization, the study found that anemia was associated with longer hospital stay, higher pneumonia severity, increased complications rate, and higher mortality rate of 11.9% overall. Conclusion Anemia in CAP patients is not merely a comorbidity but is associated with poor prognosis and increased risk for complications and mortality. Community acquired pneumonia anemia mortality prognosis Figures Figure 1 Figure 2 Introduction Community-acquired pneumonia (CAP) is a significant cause of mortality, particularly in hospitalized cases 1 , and is the second most frequent cause of hospital admission 2,3 . Mortality rates in severe cases range from 5% to 30-50% 4 in critically ill hospitalized patients. Risk factors include conditions that compromise immune mechanisms such as lifestyle (smoking, alcohol), chronic diseases (diabetes, tumors, COPD), and immunodeficiency 5 . Despite advances in diagnosis and treatment, community-acquired pneumonia (CAP) remains the leading cause of morbidity and mortality, especially in cases requiring hospitalization 1 . Several indicators have been used to predict the prognosis of CAP, including PSI and CURB-65. Assessing pneumonia severity is crucial for determining the treatment location, and scores like PSI (Pneumonia Severity Index) and CURB-65 are used 6 . The PSI score stratifies patients into five groups based on 20 variables 7 . Symptoms and signs associated with increased mortality include dyspnea, chills, altered mental status, fever, tachypnea, and hypotension. Laboratory and radiological findings include hyponatremia, hyperglycemia, elevated BUN, low albumin, hypoxemia, elevated liver enzymes, and pleural effusion 8 . The Infectious Diseases Society of America (IDSA) recommends extensive pathogen investigation, while the American Thoracic Society (ATS) recommends initiating empirical treatment 8,9 . Streptococcus pneumoniae is the most common cause of CAP 10 . Common clinical symptoms include cough, fever, chills, fatigue, dyspnea, and pleuritic pain 11 . A new infiltrate on a chest X-ray is essential for diagnosing pneumonia 12 . Identifying the causative pathogen is necessary to guide antibiotic treatment 13 . However, Sputum Gram stain and culture of respiratory secretions are recommended in severe pneumonia or when specific risk factors are present 14 . After diagnosis, the treatment location and appropriate antibiotic must be determined 15 . Antibiotics are recommended for all patients, and treatment should ideally begin within 3-4 hours of diagnosis 16 . Anemia is a global health problem affecting all ages 17 . It is diagnosed by hemoglobin levels below the normal range for age and gender 17 . The World Health Organization (WHO) defines anemia as hemoglobin values ˂12.0 g/dL for women or ˂13.0 g/dL for men 18 . Anemia of Inflammation (AI), which develops within days of disease onset 19 , is the most common type of anemia in hospitalized patients, surpassed only to Iron Deficiency Anemia 20 . Inflammation is a biological response and part of the body's defense mechanisms, aiming to mitigate harmful effects 21 . Acute inflammation leads to reduced iron availability for red blood cell formation 22 . Anemia is classified by severity into four severity group 23 . Epidemiological studies show its association with poor prognosis in many diseases, especially in the elderly 24 . Approximately one-third of the world's population (32.9%) suffers from anemia 25 . According to pathogenic mechanism, anemia is classified to: reduced red blood cell production, red blood cell loss, or both 26 . AI occurs through three pathogenic mechanisms: restricted iron access (iron sequestration in macrophages and reduced absorption) 27 , inhibition of erythropoiesis 28 , and reduced red blood cell lifespan 29,30 , in addition, the body sequesters iron as part of innate immunity 31 . Common symptoms of anemia include weakness, fatigue, dizziness, presyncope, syncope, dyspnea, and chest pain 32 . Red blood cells in AI are often normocytic and normochromic but can become hypochromic and microcytic with increasing severity 33 . Serum iron concentration decreases, and ferritin increases in AI 34 . AI leads to increased disease severity and complications 35 , furthermore, the presence of anemia is associated with an increased length of hospital stay 36 . Iron is crucial for both human health and pathogens 37 , however, caution is advised when treating anemia in inflammatory conditions, and the underlying cause should be addressed 38 . The prevalence of Anemia in Community Acquired Pneumonia (CAP): Anemia represents a significant and highly prevalent hematologic comorbidity among patients hospitalized with acute infections, notably Community-Acquired Pneumonia (CAP). Published studies consistently report high rates of anemia affecting approximately 30% to over 60% of CAP patients at some point during their hospital stay 39 . The etiology of anemia in this acute setting is predominantly the Anemia of Inflammation (AI), a systemic response that compromises iron utilization and erythropoiesis 28 rather than being due to acute blood loss. The core pathophysiology is initiated by the release of pro-inflammatory cytokines 40 , such as interleukin-6 (IL-6), which characterize the acute phase reaction in pneumonia. IL-6 subsequently drives the hepatic synthesis of hepcidin, the master regulator of iron homeostasis. Elevated hepcidin levels induce functional iron deficiency by triggering the internalization and degradation of the cellular iron exporter, ferroportin (FPN), found on macrophages and duodenal enterocytes 37,40 . This action effectively sequesters iron within storage cells limiting its availability for hemoglobin synthesis and resulting in iron-restricted erythropoiesis despite adequate systemic iron reserves. Inflammatory mediators further compound these effects by directly suppressing erythropoietin production and red blood cell survival 29,41 , collectively contributing to the rapid development of anemia during acute inflammatory illness. The most important determinant of mortality is not the pathogen but rather the degree and nature of the host response 42 . In overall, there is an increasing interest in studying the anemia prevalence among hospitalized patients and its consequences in comorbidity and mortality 43 .Considering that CAP is the second leading cause of hospital admission, our study aims to investigate the prevalence and progression of anemia in these patients, and its relationship with hospital stay, complications, mortality, and pneumonia severity. Study Design, Site, and Participants This was a single-center prospective observational cohort study conducted at Latakia University Hospital, Latakia, Syria, between February 2024 and February 2025. We consecutively enrolled 60 adult patients (aged ≥18 years) who were hospitalized with confirmed Community-Acquired Pneumonia (CAP). CAP diagnosis required a new, radiologically-confirmed pulmonary infiltrate on chest X-ray combined with compatible clinical signs and symptoms. Exclusion Criteria: Patients were excluded if they had pneumonia within the past 30 days, patients who require chronic mechanical ventilation, patients diagnosed with cystic fibrosis or pulmonary tuberculosis, and pregnancy. We also excluded pre-existing diagnosis of a hematological disorder (e.g., leukemia, myelodysplastic syndrome), chronic gastrointestinal bleeding, or any other known cause of anemia unrelated to acute inflammation. Clinical Definitions and Data Collection Data Collection: Detailed baseline clinical, demographic, and laboratory information was collected prospectively using a structured questionnaire and medical record review; The questionnaire developed for this study is provided as Supplementary File 1. Anemia Definition: Anemia was defined according to the World Health Organization (WHO) 18 gender-specific criteria: Men: Hemoglobin (Hgb < 13 g/dL) Women: Hemoglobin (Hgb WHO cutoff (gender-specific) Mild Anemia: Hgb 10-12 g/dl Moderate Anemia: Hgb 8-10 g/dL Severe Anemia: Hgb 6.5-7.9 g/dL Life-threatening: Hgb < 6.5 g/dL Hemoglobin Measurement Time Points: Hemoglobin levels were measured sequentially at four specific time points during the hospitalization: Admission: Within 24 hours of hospital admission. Day 4: Approximately 72 hours after admission. Day 7: Approximately 144 hours after admission. Discharge: Within 48 hours prior to patient discharge. Outcome Variables: Pneumonia Severity: Assessed using the Pneumonia Severity Index (PSI). For analytical purposes, PSI classes III, IV, and V were aggregated into a single "High-Risk" group. Primary Outcomes: Length of Hospital Stay (LOHS) (measured in days) and In-Hospital Mortality. Secondary Outcome: In-hospital Complications (defined as the occurrence of treatment failure, septic shock, ICU admission, mechanical ventilation requirement, or need for blood transfusion). Post-Discharge Follow-up: Post-discharge outcomes could not be determined within the scope of this study. Statistical Analysis Statistical analyses were performed using IBM SPSS Statistics, version 25.0. The level of statistical significance was set at < 0.05 for all tests. Descriptive Statistics: Quantitative variables are expressed as mean ± standard deviation (SD), while qualitative variables are Reported as frequencies and percentages ( n, % ) . Inferential Statistics: Comparison of Categorical Data: The Chi-square test or Fisher's exact test was used to examine the relationships between qualitative variables (e.g., anemia status vs. mortality). Comparison of Means (Two Groups): The Independent Samples t -test was used to study differences in means between two independent groups (e.g., LOHS between anemic and non-anemic patients). Comparison of Repeated Measures: The Friedman test was employed to compare the mean Hgb levels across the four measurement time points (Admission, Day 4, Day 7, Discharge). Results Baseline Characteristics: A total of 60 adult patients hospitalized with Community-Acquired Pneumonia (CAP) were enrolled. The mean age of the cohort was 55.4 ± 20.1 years. Males constituted the majority of the patients (35/60; 58.3%). Regarding risk factors and comorbidities, 66.7% (40/60) were current smokers, and 46.7% (28/60) had at least one pre-existing comorbidity, with hypertension (31.6%) and chronic lung diseases (31.6%) being the most prevalent. Anemia Prevalence and Progression: The overall prevalence of anemia (defined by WHO gender-specific criteria) was high across the hospitalization period. On Admission: 71.7% (43/60) of patients were classified as anemic. At Discharge: The prevalence increased to 86.7% (52/60). Anemia severity on admission was predominantly mild (Hgb 10-12 g/dL), affecting 58.3% of the cohort. Sequential hemoglobin measurements at admission, Day 4, Day 7, and discharge show no statistically significant change in the mean Hgb level over the hospitalization course (P=0.7). No statistically significant association was found between the presence of anemia (on admission) and the patient’s gender (P=0.6). Table (1): Baseline Characteristics of Study Participants Characteristic Value Notes Age, years 55.3±20.1 Means ± Standard Deviation Gender, n (%) Male Female 35(58.3%) 25 (41.7%) Age group 18 – 39 40 – 64 ≥ 65 14 (23.3%) 29 (48.3%) 17 (28.3%) Smoking status, n (%) Smoker Non-smoker 40 (66.7%) 20 (33.3%) Cigarettes 37 (61.7%) Hookah 3 (5%) Symptoms, n (%) Cough Dyspnea Fever Chest Pain Hemoptysis 48 (80%) 43 (71.7%) 42 (70%) 21 (35%) 5 (8.3%) Comorbidities, n (%) Hypertension Lung diseases COPD Asthma Lung fibrosis Diabetes Mellitus Heart Failure Renal Diseases 19 (31.9%) 19 (31.9%) 11 (18.3%) 6 (10%) 2 (3.3%) 15 (25%) 15 (25%) 4 (6.7%) Antibiotic Use Prior to admission, n (%) 20 (33.3%) Complications, n (%) Treatment Failure Death ICU Admission Septic Shock Blood Transfusion Mechanical Ventilation 16 (26.7%) 7 (11.7%) 6 (10%) 3 (5%) 1 (1.7%) 1 (1.7%) PSI Severity Class, n (%) I II III – V 14 (23.3%) 15 (25%) 31 (51,7%) Association of Anemia with Disease Severity: Anemia status on admission was highly associated with the Pneumonia Severity Index (PSI) risk classification (P < 0.001). Anemic patients were significantly more likely to be classified in the high-risk group (Classes III-V ) , while 59.6% (31/52) falling into this category, compared to 0% (0/8) of non-anemic patients. Conversely, 87.5% (7/8) of non-anemic patients were in the lowest risk group (Class I), compared to only 13.5% (7/52) of anemic patients. Association of Anemia with Outcomes: 1) Length of Hospital Stay (LOHS): Anemic patients experienced a significantly longer hospitalization period compared to non-anemic patients (P=0.001). The mean (LOHS) for anemic patients was 12.8 ± 7.5 days, which was substantially longer than the mean (LOHS) for non-anemic patients 5.4 ± 2.1 days. 2) In-Hospital Complications: The overall incidence of at least one in-hospital complication (e.g., treatment failure, ICU admission, septic shock, blood transfusion, or mechanical ventilation) was 41.7% (25/60). The incidence of complications was significantly higher among anemic patients (46.2% or 24/52) compared to non-anemic patients (12.5% or 1/8) (P=0.002). Discussion Prevalence of anemia in CAP patients : An initial anemia prevalence of 71.7% was observed on admission, increasing to 86.7% by discharge. This high percentage of anemia reflects its widespread, especially in Low- and Middle-Income Countries (LMICs), and remains a global health problem 26 . While some studies, such as Reade et al. 39 , documented a statistically significant development or worsening of anemia during hospitalization, our serial measurements did not show a significant change in anemia prevalence or severity over time (P=0.7). Despite this difference in timing, our results align with the broader consensus that the presence of anemia is critical factor. Its strong association with a prolonged hospitalization, higher complication rates, and significantly increased mortality underscores that anemia is a potent marker of severe disease and poor prognosis in CAP 39,44 . Therefore, whether developing during the stay or present on admission, anemia serves as a crucial clinical red flag, identifying patients who require escalated care and management to potentially improve their outcomes. The analysis of pneumonia severity : Pneumonia severity as stratified by the pneumonia severity index (PSI), revealed a profound and highly statistically significant disparity between anemic and non-anemic patients (P<0.0001). The data demonstrates a clear gradient: the anemic patient cohort was overwhelmingly classified within the high-risk PSI classes (III -V), whereas the non-anemic cohort was predominantly comprised of low-risk patient’s classes (I -II). This powerful association indicates that the presence of anemia-whether pre-existing or emerging very early in the disease course - is intrinsically linked to more severe manifestations of community-acquired pneumonia. 39 Therefore, the detection of anemia at admission can be considered a rapid and practical clinical correlate to a high PSI score, serving as an immediate red flag to identify those patients who are at a significantly elevated risk for a complicated hospital course and who may require more intensive management from the outset. Impact of anemia in clinical outcomes: In hospital complications included treatment failure, death, ICU admission, septic shock, blood transfusion, and mechanical ventilation. In our study complications were significantly more frequent among anemic patients (46.2%) compared to those without anemia (12.5%, P=0.002). Although anemia is part of the host’s immune response in pneumonia - aimed at restricting iron from pathogens 37 – it may also impair oxygen delivery in critically inflamed state. This could explain the high rate of complications (46.2%) observed in anemic patients. The most compelling finding of this study is the stark contrast in mortality outcomes based on hematological status. All fatalities in cohort (11.7%) occurred exclusively among patients who had anemia during their hospitalization. This resulted in a mortality rate of (13.5%) in the anemic group compared to (0%) in the non-anemic group, an association that was highly statistically significant (P<0.001). This powerful correlation suggests that the development of anemia or the presence of anemia in CAP patients is not merely an epiphenomenon but a potent marker of critical illness and a strong independent predictor of fatal outcome 43,44 . The pathophysiological link may be explained by a severe systemic inflammatory response suppressing erythropoiesis and reducing iron availability 37 , coupled with a diminished oxygen-carrying capacity that exacerbates tissue hypoxia in vital organs 45 . This can precipitate multi-organ failure, which is a likely final common pathway for these patients. Our analysis revealed that the length of stay was markedly prolonged for patients who developed anemia, with a mean of 13.1 ± 7.2 days, compared to only 5.4 ± 2.1 days for those who did not (P<0.001). This more than twofold increase in hospitalization time is not only statistically robust but also carries substantial clinical and economic implications. The Receiver Operating Characteristic (ROC) curve analysis presented in Figure 1 revealed an Area Under the Curve (AUC) of 0.64 (P=0.001) for hemoglobin as a predictor of disease severity. While statistically significant, an AUC of 0.64 suggests a modest predictive capability for hemoglobin alone. An AUC value of 0.7 is typically considered the minimum threshold for a 'fair' predictor, indicating that hemoglobin, while informative, may not be a standalone, highly accurate indicator of CAP severity in this cohort. The optimal predictive threshold identified was a hemoglobin level of 10.25 g/dL. This value is particularly relevant as it falls within the standard definitions of anemia, reinforcing the clinical significance of anemia in stratifying patient risk. The modest predictive value underscores the complexity of CAP severity, which is influenced by multiple factors beyond a single hematological parameter. Table (2): Association of Anemia Status with Clinical Outcomes and Patient Demographics Outcome Anemic patients (n=52) Non-anemic patients (n=8) P-value Length of Hospital Stay (LOHS), days 13.1±7.2 5.4±2.1 <0.001 Complications, n (%) Death 24 (46.2%) 7 (13.5%) 1 (12.5%) 0 (0%) <0.04 <0.001 PSI Class, n (%) I II III-V 7(13.5%) 14 (26.9%) 30 (57.7%) 7 (87.5%) 1 (12.5%) 0 (0%) <0.0001 Gender, n (%) Males Females 31 (59.6%) 21 (40.4%) 4 (50%) 4 (50%) 0.6 The development of anemia during hospitalization for CAP was not found to be influenced by patient gender. Our analysis revealed that among the 52 anemic patients, 31(59.6%) were male and 21 (40.4%) were female. This distribution was not significantly different from the non-anemic group, which consisted of 4 males (50%) and 4 females (50%) (P=0.6). The lack of a statistically significant association indicates that male and female patients were equally susceptible to development anemia in the context of their pneumonic illness, in contrast to Reade study which demonstrate that female gender was a risk factor for developing anemia in CAP patients 39 . This finding suggests that the pathophysiological mechanisms driving anemia in CAP--such as inflammation, nutritional deficits, or other illness- related factors—are likely operative across both genders and that the potent prognostic value of anemia for worse outcomes is applicable to all patients, irrespective of sex. Limitations: Our study has several limitations that warrant consideration. First, this single-center study with a relatively small sample size (n=60) may limit the generalizability of the findings and increase the risk of Type II errors for less common outcomes. Second, we could not determine the specific etiology of the anemia (e.g., iron deficiency versus anemia of chronic inflammation), which could affect the appropriate management strategy. Future studies should incorporate markers of iron status (ferritin, transferrin saturation) to better classify the type of anemia present. Finally, the inability to track post-discharge outcomes limits our understanding of long-term survival and readmission rates. Conclusion Anemia is exceptionally common in hospitalized CAP patients and is strongly associated with longer hospitalization, higher complication rates, higher mortality rates, and higher disease severity scores (as measured by the Pneumonia Severity Index (PSI)). These findings demonstrate that anemia is not simply a comorbidity but rather a poor prognostic marker. The high prevalence of anemia among pneumonia patients in our study supports the idea that the body's immune response to a pathogen decrease circulating iron, and the persistence of anemia after discharge reflects long-term mechanisms of iron retention as part of the immune response. Further research is warranted to assess whether aggressive management of anemia in this setting can improve clinical outcomes. Abbreviations AI: Anemia of Inflammation AUC: Area Under the Curve BUN: Blood Urea Nitrogen CAP: Community-Acquired Pneumonia Hgb: Hemoglobin PSI: Pneumonia Severity Index LMICs: Low- and Middle- Income Countries LOHS: Length of Hospital Stay ROC: Receiver Operating Characteristic WHO: World Health Organization Declarations Ethics Approval and Consent to Participate: The study protocol was approved by the Ethics Committee of Latakia University and Latakia University Hospital. The study was conducted in accordance with the Declaration of Helsinki. Written informed consent was obtained from all participants or their legally authorized representatives prior to enrollment. Consent for Publication: Not applicable. Availability of Data and Materials: Available from the corresponding author on reasonable request. Competing Interest: The authors declare that they have no competing interests. Funding: No specific funding was received for this study. Clinical Trial Registration: Clinical trial number: not applicable. Authors’ Contributions: Rwa Alzhraa Zreik contributed to the conceptualization, study design, and methodology. She was also responsible for drafting the main manuscript text (abstract, introduction, results, and discussion) and collaborated on the preparation and critical review of the study's results, tables, and figures. Malek Hijazeah contributed to the conceptualization, study design, and methodology. Feras Hussein collaborated on the preparation and critical review of the study's results, tables, and figures. 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Iron deficiency and infection: another pathway to explore in critically ill patients? Intensive Care Med . 2018;44(12):2260-2262. doi:10.1007/s00134-018-5438-8 Aird WC. The Hematologic System as a Marker of Organ Dysfunction in Sepsis. Mayo Clin Proc . 2003;78(7):869-881. doi:10.4065/78.7.869 Spence RK. Medical and economic impact of anemia in hospitalized patients. American Journal of Health-System Pharmacy . 2007;64(16_Supplement_11):S3-S10. doi:10.2146/ajhp070244 Kassaw G, Mohammed R, Tessema GM, Yesuf T, Lakew AM, Tarekegn GE. Outcomes and Predictors of Severe Community-acquired Pneumonia Among Adults Admitted to the University of Gondar Comprehensive Specialized Hospital: A Prospective Follow-up Study. Infect Drug Resist . 2023;Volume 16:619-635. doi:10.2147/IDR.S392844 Vincent JL. Anemia and Blood Transfusion in Critically Ill Patients. JAMA . 2002;288(12):1499. doi:10.1001/jama.288.12.1499 Additional Declarations No competing interests reported. Supplementary Files questionnaire.pdf Cite Share Download PDF Status: Under Review Version 1 posted Reviewers invited by journal 24 Dec, 2025 Editor assigned by journal 22 Dec, 2025 Editor invited by journal 01 Dec, 2025 Submission checks completed at journal 01 Dec, 2025 First submitted to journal 01 Dec, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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1","display":"","copyAsset":false,"role":"figure","size":62772,"visible":true,"origin":"","legend":"\u003cp\u003eReceiver Operating Characteristic (ROC) curve for hemoglobin as a predictor of disease severity. The Area Under the Curve (AUC) was 0.64 (P=0.001). The best predictive threshold was a hemoglobin level of 10.25 g/dl.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-7957203/v1/2c56b8cc182b1fb5e481fa13.png"},{"id":99318782,"identity":"5ac8f88b-7be4-4af0-990d-27906836d3b0","added_by":"auto","created_at":"2025-12-31 16:34:41","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":34339,"visible":true,"origin":"","legend":"\u003cp\u003eAnemia progression during hospitalization by severity category\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-7957203/v1/948a9e8e8ac2cf185f01d987.png"},{"id":99323805,"identity":"20f4645f-9883-403e-8bd2-c78e13bb386e","added_by":"auto","created_at":"2025-12-31 16:46:18","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1245357,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7957203/v1/dec2aa5d-a2d7-43ef-abfb-1c449754d0a7.pdf"},{"id":99319798,"identity":"ea4ec41c-bfe0-4b33-83af-bf16afc4e3f9","added_by":"auto","created_at":"2025-12-31 16:37:52","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":181407,"visible":true,"origin":"","legend":"","description":"","filename":"questionnaire.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7957203/v1/0e5d36ac839e296d1956b27c.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"The prevalence and development of anemia in community- acquired pneumonia patients and its association with the duration of hospitalization and mortality","fulltext":[{"header":"Introduction","content":"\u003cp\u003eCommunity-acquired pneumonia (CAP) is a significant cause of mortality, particularly in hospitalized cases \u003csup\u003e1\u003c/sup\u003e, and is the second most frequent cause of hospital admission \u003csup\u003e2,3\u003c/sup\u003e. Mortality rates in severe cases range from 5% to 30-50% \u003csup\u003e4\u003c/sup\u003e in critically ill hospitalized patients. Risk factors include conditions that compromise immune mechanisms such as lifestyle (smoking, alcohol), chronic diseases (diabetes, tumors, COPD), and immunodeficiency \u003csup\u003e5\u003c/sup\u003e.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eDespite advances in diagnosis and treatment, community-acquired pneumonia (CAP) remains the leading cause of morbidity and mortality, especially in cases requiring hospitalization\u003csup\u003e1\u003c/sup\u003e. \u0026nbsp;Several indicators have been used to predict the prognosis of CAP, including PSI and CURB-65. Assessing pneumonia severity is crucial for determining the treatment location, and scores like PSI (Pneumonia Severity Index) and CURB-65 are used \u003csup\u003e6\u003c/sup\u003e. The PSI score stratifies patients into five groups based on 20 variables \u003csup\u003e7\u003c/sup\u003e. Symptoms and signs associated with increased mortality include dyspnea, chills, altered mental status, fever, tachypnea, and hypotension. Laboratory and radiological findings include hyponatremia, hyperglycemia, elevated BUN, low albumin, hypoxemia, elevated liver enzymes, and pleural effusion \u003csup\u003e8\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eThe Infectious Diseases Society of America (IDSA) recommends extensive pathogen investigation, while the American Thoracic Society (ATS) recommends initiating empirical treatment \u003csup\u003e8,9\u003c/sup\u003e. Streptococcus pneumoniae is the most common cause of CAP \u003csup\u003e10\u003c/sup\u003e. Common clinical symptoms include cough, fever, chills, fatigue, dyspnea, and pleuritic pain \u003csup\u003e11\u003c/sup\u003e. A new infiltrate on a chest X-ray is essential for diagnosing pneumonia \u003csup\u003e12\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eIdentifying the causative pathogen is necessary to guide antibiotic treatment \u003csup\u003e13\u003c/sup\u003e. However, Sputum Gram stain and culture of respiratory secretions are recommended in severe pneumonia or when specific risk factors are present \u003csup\u003e14\u003c/sup\u003e. After diagnosis, the treatment location and appropriate antibiotic must be determined \u003csup\u003e15\u003c/sup\u003e. Antibiotics are recommended for all patients, and treatment should ideally begin within 3-4 hours of diagnosis \u003csup\u003e16\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAnemia\u003c/strong\u003e is a global health problem affecting all ages \u003csup\u003e17\u003c/sup\u003e. It is diagnosed by hemoglobin levels below the normal range for age and gender \u003csup\u003e17\u003c/sup\u003e. The World Health Organization (WHO) defines anemia as hemoglobin values ˂12.0 g/dL for women or ˂13.0 g/dL for men \u003csup\u003e18\u003c/sup\u003e. Anemia of Inflammation (AI), which develops within days of disease onset \u003csup\u003e19\u003c/sup\u003e, is the most common type of anemia in hospitalized patients, surpassed only to Iron Deficiency Anemia \u003csup\u003e20\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eInflammation is a biological response and part of the body's defense mechanisms, aiming to mitigate harmful effects \u003csup\u003e21\u003c/sup\u003e. Acute inflammation leads to reduced iron availability for red blood cell formation \u003csup\u003e22\u003c/sup\u003e. Anemia is classified by severity into four severity group\u003csup\u003e23\u003c/sup\u003e. Epidemiological studies show its association with poor prognosis in many diseases, especially in the elderly \u003csup\u003e24\u003c/sup\u003e. Approximately one-third of the world's population (32.9%) suffers from anemia \u003csup\u003e25\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eAccording to pathogenic mechanism, anemia is classified to: reduced red blood cell production, red blood cell loss, or both \u003csup\u003e26\u003c/sup\u003e. AI occurs through three pathogenic mechanisms: restricted iron access (iron sequestration in macrophages and reduced absorption) \u003csup\u003e27\u003c/sup\u003e, inhibition of erythropoiesis \u003csup\u003e28\u003c/sup\u003e, and reduced red blood cell lifespan \u003csup\u003e29,30\u003c/sup\u003e, in addition, the body sequesters iron as part of innate immunity \u003csup\u003e31\u003c/sup\u003e. Common symptoms of anemia include weakness, fatigue, dizziness, presyncope, syncope, dyspnea, and chest pain \u003csup\u003e32\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eRed blood cells in AI are often normocytic and normochromic but can become hypochromic and microcytic with increasing severity \u003csup\u003e33\u003c/sup\u003e. Serum iron concentration decreases, and ferritin increases in AI \u003csup\u003e34\u003c/sup\u003e. AI leads to increased disease severity and complications \u003csup\u003e35\u003c/sup\u003e, furthermore, the presence of anemia is associated with an increased length of hospital stay \u003csup\u003e36\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eIron is crucial for both human health and pathogens \u003csup\u003e37\u003c/sup\u003e, however, caution is advised when treating anemia in inflammatory conditions, and the underlying cause should be addressed \u003csup\u003e38\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eThe prevalence of Anemia in Community Acquired Pneumonia (CAP):\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAnemia represents a significant and highly prevalent hematologic comorbidity among patients hospitalized with acute infections, notably Community-Acquired Pneumonia (CAP). Published studies consistently report high rates of anemia affecting approximately 30% to over 60% of CAP patients at some point during their hospital stay\u003csup\u003e39\u003c/sup\u003e. The etiology of anemia in this acute setting is predominantly the Anemia of Inflammation (AI), a systemic response that compromises iron utilization and erythropoiesis\u003csup\u003e28\u003c/sup\u003e rather than being due to acute blood loss. The core pathophysiology is initiated by the release of pro-inflammatory cytokines\u003csup\u003e40\u003c/sup\u003e, such as interleukin-6 (IL-6), which characterize the acute phase reaction in pneumonia. IL-6 subsequently drives the hepatic synthesis of hepcidin, the master regulator of iron homeostasis. Elevated hepcidin levels induce functional iron deficiency by triggering the internalization and degradation of the cellular iron exporter, ferroportin (FPN), found on macrophages and duodenal enterocytes \u003csup\u003e37,40\u003c/sup\u003e. This action effectively sequesters iron within storage cells limiting its availability for hemoglobin synthesis and resulting in iron-restricted erythropoiesis despite adequate systemic iron reserves. Inflammatory mediators further compound these effects by directly suppressing erythropoietin production and red blood cell survival\u003csup\u003e29,41\u003c/sup\u003e, collectively contributing to the rapid development of anemia during acute inflammatory illness.\u003c/p\u003e\n\u003cp\u003eThe most important determinant of mortality is not the pathogen but rather the degree and nature of the host response\u003csup\u003e42\u003c/sup\u003e. In overall,\u0026nbsp;there is an increasing interest in studying the anemia prevalence among hospitalized patients and its consequences in comorbidity and mortality\u003csup\u003e43\u003c/sup\u003e.Considering that CAP is the second leading cause of hospital admission, our study aims to investigate the prevalence and progression of anemia in these patients, and its relationship with hospital stay, complications, mortality, and pneumonia severity.\u003c/p\u003e\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n"},{"header":"Study Design, Site, and Participants","content":"\u003cp\u003eThis was a single-center prospective observational cohort study conducted at Latakia University Hospital, Latakia, Syria, between February 2024 and February 2025.\u003c/p\u003e\u003cp\u003eWe consecutively enrolled 60 adult patients (aged ≥18 years) who were hospitalized with confirmed Community-Acquired Pneumonia (CAP). CAP diagnosis required a new, radiologically-confirmed pulmonary infiltrate on chest X-ray combined with compatible clinical signs and symptoms.\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eExclusion Criteria:\u003c/strong\u003e Patients were excluded if they had pneumonia within the past 30 days, patients who require chronic mechanical ventilation, patients diagnosed with cystic fibrosis or pulmonary tuberculosis, and pregnancy. We also excluded pre-existing diagnosis of a hematological disorder (e.g., leukemia, myelodysplastic syndrome), chronic gastrointestinal bleeding, or any other known cause of anemia unrelated to acute inflammation.\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eClinical Definitions and Data Collection\u003c/strong\u003e\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eData Collection:\u003c/strong\u003e Detailed baseline clinical, demographic, and laboratory information was collected prospectively using a structured questionnaire and medical record review; The questionnaire developed for this study is provided as Supplementary File 1.\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eAnemia Definition:\u003c/strong\u003e Anemia was defined according to the World Health Organization (WHO)\u003csup\u003e18\u003c/sup\u003e gender-specific criteria:\u003c/p\u003e\u003cul type=\"disc\"\u003e\n \u003cli\u003e\u003cstrong\u003eMen:\u003c/strong\u003e Hemoglobin (Hgb \u0026lt; 13 g/dL)\u003c/li\u003e\n \u003cli\u003e\u003cstrong\u003eWomen:\u003c/strong\u003e Hemoglobin (Hgb \u0026lt; 12 g/dL)\u003c/li\u003e\n\u003c/ul\u003e\u003cp\u003e\u003cstrong\u003eAnemia Severity Classification:\u003c/strong\u003e after identifying anemia according to WHO, we classified the anemia severity based on absolute Hgb values\u003csup\u003e23\u003c/sup\u003e:\u003c/p\u003e\u003cul type=\"disc\"\u003e\n \u003cli\u003e\u003cstrong\u003eNo Anemia:\u003c/strong\u003e Hgb \u0026gt; WHO cutoff (gender-specific)\u003c/li\u003e\n \u003cli\u003e\u003cstrong\u003eMild Anemia:\u003c/strong\u003e Hgb 10-12 g/dl\u003c/li\u003e\n \u003cli\u003e\u003cstrong\u003eModerate Anemia:\u003c/strong\u003e Hgb 8-10 g/dL\u003c/li\u003e\n \u003cli\u003e\u003cstrong\u003eSevere Anemia:\u0026nbsp;\u003c/strong\u003eHgb 6.5-7.9 g/dL\u003c/li\u003e\n \u003cli\u003e\u003cstrong\u003eLife-threatening:\u003c/strong\u003e Hgb \u0026lt; 6.5 g/dL\u003c/li\u003e\n\u003c/ul\u003e\u003cp\u003e\u003cstrong\u003eHemoglobin Measurement Time Points:\u003c/strong\u003e Hemoglobin levels were measured sequentially at four specific time points during the hospitalization:\u003c/p\u003e\u003col start=\"1\" type=\"1\"\u003e\n \u003cli\u003e\u003cstrong\u003eAdmission:\u003c/strong\u003e Within 24 hours of hospital admission.\u003c/li\u003e\n \u003cli\u003e\u003cstrong\u003eDay 4:\u003c/strong\u003e Approximately 72 hours after admission.\u003c/li\u003e\n \u003cli\u003e\u003cstrong\u003eDay 7:\u003c/strong\u003e Approximately 144 hours after admission.\u003c/li\u003e\n \u003cli\u003e\u003cstrong\u003eDischarge:\u003c/strong\u003e Within 48 hours prior to patient discharge.\u003c/li\u003e\n\u003c/ol\u003e\u003cp\u003e\u003cstrong\u003eOutcome Variables:\u003c/strong\u003e\u003c/p\u003e\u003cul type=\"disc\"\u003e\n \u003cli\u003e\u003cstrong\u003ePneumonia Severity:\u003c/strong\u003e Assessed using the Pneumonia Severity Index (PSI). For analytical purposes, PSI classes III, IV, and V were aggregated into a single \"High-Risk\" group.\u003c/li\u003e\n \u003cli\u003e\u003cstrong\u003ePrimary Outcomes:\u003c/strong\u003e Length of Hospital Stay (LOHS) (measured in days) and In-Hospital Mortality.\u003c/li\u003e\n \u003cli\u003e\u003cstrong\u003eSecondary Outcome:\u003c/strong\u003e In-hospital Complications (defined as the occurrence of treatment failure, septic shock, ICU admission, mechanical ventilation requirement, or need for blood transfusion).\u003c/li\u003e\n \u003cli\u003e\u003cstrong\u003ePost-Discharge Follow-up:\u003c/strong\u003e Post-discharge outcomes could not be determined within the scope of this study.\u003c/li\u003e\n\u003c/ul\u003e\u003cp\u003e\u003cstrong\u003eStatistical Analysis\u003c/strong\u003e\u003c/p\u003e\u003cp\u003eStatistical analyses were performed using IBM SPSS Statistics, version 25.0. The level of statistical significance was set at \u0026lt; 0.05 for all tests.\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eDescriptive Statistics:\u003c/strong\u003e Quantitative variables\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003eare expressed as mean\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e± standard deviation\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e(SD), while qualitative variables are Reported as frequencies and percentages\u003cstrong\u003e\u0026nbsp;(\u003c/strong\u003en, %\u003cstrong\u003e)\u003c/strong\u003e.\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eInferential Statistics:\u003c/strong\u003e \u003cstrong\u003eComparison of Categorical Data:\u003c/strong\u003e The Chi-square\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003etest or Fisher's exact test was used to examine the relationships between qualitative variables (e.g., anemia status vs. mortality). \u003cstrong\u003eComparison of Means (Two Groups):\u003c/strong\u003e The Independent Samples\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003et\u003cstrong\u003e-test\u003c/strong\u003e was used to study differences in means between two independent groups (e.g., LOHS between anemic and non-anemic patients). \u003cstrong\u003eComparison of Repeated Measures:\u003c/strong\u003e The Friedman test was employed to compare the mean Hgb levels across the four measurement time points (Admission, Day 4, Day 7, Discharge).\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003eBaseline Characteristics: A total of 60 adult patients hospitalized with Community-Acquired Pneumonia (CAP) were enrolled. The mean age of the cohort was 55.4 \u0026plusmn; 20.1 years. Males constituted the majority of the patients (35/60; 58.3%). Regarding risk factors and comorbidities, 66.7% (40/60) were current smokers, and 46.7% (28/60) had at least one pre-existing comorbidity, with hypertension (31.6%) and chronic lung diseases (31.6%) being the most prevalent.\u003c/p\u003e\n\u003cp\u003eAnemia Prevalence and Progression: The overall prevalence of anemia (defined by WHO gender-specific criteria) was high across the hospitalization period. On Admission: 71.7% (43/60) of patients were classified as anemic. At Discharge: The prevalence increased to 86.7% (52/60). Anemia severity on admission was predominantly mild (Hgb 10-12 g/dL), affecting 58.3% of the cohort. Sequential hemoglobin measurements at admission, Day 4, Day 7, and discharge show no statistically significant change in the mean Hgb level over the hospitalization course (P=0.7). No statistically significant association was found between the presence of anemia (on admission) and the patient\u0026rsquo;s gender (P=0.6).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable (1): Baseline Characteristics of Study Participants\u003c/strong\u003e\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 170px;\"\u003e\u003cstrong\u003eCharacteristic\u003c/strong\u003e\u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 96px;\"\u003e\u003cstrong\u003eValue\u003c/strong\u003e\u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 184px;\"\u003e\u003cstrong\u003eNotes\u003c/strong\u003e\u003cbr\u003e\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 170px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eAge, years\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 96px;\"\u003e\n \u003cp\u003e55.3\u0026plusmn;20.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 184px;\"\u003e\n \u003cp\u003eMeans \u0026plusmn; Standard Deviation\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 170px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eGender, n (%)\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003eMale\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eFemale \u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 96px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e35(58.3%)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e25 (41.7%)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 184px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 170px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eAge group\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e18 \u0026ndash; 39\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e40 \u0026ndash; 64\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026ge; 65\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 96px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e14 (23.3%)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e29 (48.3%)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e17 (28.3%)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 184px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 170px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eSmoking status, n (%)\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eSmoker\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eNon-smoker\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 96px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e40 (66.7%)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e20 (33.3%)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 184px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eCigarettes 37 (61.7%)\u003c/p\u003e\n \u003cp\u003eHookah \u0026nbsp; \u0026nbsp; 3 (5%)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 170px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eSymptoms, n (%)\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003eCough\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eDyspnea\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eFever\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eChest Pain\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eHemoptysis \u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 96px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e48 (80%)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e43 (71.7%)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e42 (70%)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e21 (35%)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e5 (8.3%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 184px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 170px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eComorbidities, n (%)\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eHypertension\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eLung diseases\u003c/p\u003e\n \u003cul\u003e\n \u003cli\u003eCOPD\u003c/li\u003e\n \u003cli\u003eAsthma\u0026nbsp;\u003c/li\u003e\n \u003cli\u003eLung fibrosis\u003c/li\u003e\n \u003c/ul\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eDiabetes Mellitus\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eHeart Failure\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eRenal Diseases\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 96px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e19 (31.9%)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e19 (31.9%)\u003c/p\u003e\n \u003cp\u003e11 (18.3%)\u003c/p\u003e\n \u003cp\u003e6 (10%)\u003c/p\u003e\n \u003cp\u003e2 (3.3%)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e15 (25%)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e15 (25%)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e4 (6.7%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 184px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 170px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eAntibiotic Use Prior to admission, n (%)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 96px;\"\u003e\n \u003cp\u003e20 (33.3%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 184px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 170px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eComplications, n (%)\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003eTreatment Failure\u003c/p\u003e\n \u003cp\u003eDeath\u003c/p\u003e\n \u003cp\u003eICU Admission\u003c/p\u003e\n \u003cp\u003eSeptic Shock\u003c/p\u003e\n \u003cp\u003eBlood Transfusion\u003c/p\u003e\n \u003cp\u003eMechanical Ventilation\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 96px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e16 (26.7%)\u003c/p\u003e\n \u003cp\u003e7 (11.7%)\u003c/p\u003e\n \u003cp\u003e6 (10%)\u003c/p\u003e\n \u003cp\u003e3 (5%)\u003c/p\u003e\n \u003cp\u003e1 (1.7%)\u003c/p\u003e\n \u003cp\u003e1 (1.7%)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 184px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 170px;\"\u003e\n \u003cp\u003e\u003cstrong\u003ePSI Severity Class, n (%)\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eI\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eII\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eIII \u0026ndash; V\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 96px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e14 (23.3%)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e15 (25%)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e31 (51,7%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 184px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eAssociation of Anemia with Disease Severity: Anemia status on admission was highly associated with the Pneumonia Severity Index (PSI) risk classification (P \u0026lt; 0.001). Anemic patients were significantly more likely to be classified in the high-risk group (Classes III-V\u003cstrong\u003e)\u003c/strong\u003e, while 59.6% (31/52) falling into this category, compared to 0% (0/8) of non-anemic patients. Conversely, 87.5% (7/8) of non-anemic patients were in the lowest risk group (Class I), compared to only 13.5% (7/52) of anemic patients.\u003c/p\u003e\n\u003cp\u003eAssociation of Anemia with Outcomes: 1) Length of Hospital Stay (LOHS): Anemic patients experienced a significantly longer hospitalization period compared to non-anemic patients (P=0.001). The mean (LOHS) for anemic patients was 12.8 \u0026plusmn; 7.5\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003edays, which was substantially longer than the mean (LOHS) for non-anemic patients 5.4 \u0026plusmn; 2.1 days. 2) In-Hospital Complications: The overall incidence of at least one in-hospital complication (e.g., treatment failure, ICU admission, septic shock, blood transfusion, or mechanical ventilation) was 41.7% (25/60). The incidence of complications was significantly higher among anemic patients (46.2% or 24/52) compared to non-anemic patients (12.5% or 1/8) (P=0.002).\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003e\u003cstrong\u003ePrevalence of anemia in CAP patients\u003c/strong\u003e:\u003c/p\u003e\n\u003cp\u003eAn initial anemia prevalence of 71.7% was observed on admission, increasing to 86.7% by discharge. This high percentage of anemia reflects its widespread, especially in Low- and Middle-Income Countries (LMICs), and remains a global health problem\u003csup\u003e26\u003c/sup\u003e. While some studies, such as Reade et al.\u003csup\u003e39\u003c/sup\u003e, documented a statistically significant development or worsening of anemia during hospitalization, our serial measurements did not show a significant change in anemia prevalence or severity over time (P=0.7). Despite this difference in timing, our results align with the broader consensus that the presence of anemia is critical factor. Its strong association with a prolonged hospitalization, higher complication rates, and significantly increased mortality underscores that anemia is a potent marker of severe disease and poor prognosis in CAP\u003csup\u003e\u0026nbsp;\u003c/sup\u003e\u003csup\u003e39,44\u003c/sup\u003e. Therefore, whether developing during the stay or present on admission, anemia serves as a crucial clinical red flag, identifying patients who require escalated care and management to potentially improve their outcomes.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eThe analysis of pneumonia severity\u003c/strong\u003e:\u003c/p\u003e\n\u003cp\u003ePneumonia severity as stratified by the pneumonia severity index (PSI), revealed a profound and highly statistically significant disparity between anemic and non-anemic patients (P\u0026lt;0.0001). The data demonstrates a clear gradient: the anemic patient cohort was overwhelmingly classified within the high-risk PSI classes (III -V), whereas the non-anemic cohort was predominantly comprised of low-risk patient\u0026rsquo;s classes (I -II). This powerful association indicates that the presence of anemia-whether pre-existing or emerging very early in the disease course - is intrinsically linked to more severe manifestations of community-acquired pneumonia.\u003csup\u003e39\u003c/sup\u003e Therefore, the detection of anemia at admission can be considered a rapid and practical clinical correlate to a high PSI score, serving as an immediate red flag to identify those patients who are at a significantly elevated risk for a complicated hospital course and who may require more intensive management from the outset.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eImpact of anemia in clinical outcomes:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eIn hospital complications included treatment failure, death, ICU admission, septic shock, blood transfusion, and mechanical ventilation. In our study complications were significantly more frequent among anemic patients (46.2%) compared to those without anemia (12.5%, P=0.002). Although anemia is part of the host\u0026rsquo;s immune response in pneumonia - aimed at restricting iron from pathogens\u003csup\u003e37\u003c/sup\u003e \u0026ndash; it may also impair oxygen delivery in critically inflamed state. This could explain the high rate of complications (46.2%) observed in anemic patients. The most compelling finding of this study is the stark contrast in mortality outcomes based on hematological status. All fatalities in cohort (11.7%) occurred exclusively among patients who had anemia during their hospitalization. This resulted in a mortality rate of (13.5%) in the anemic group compared to (0%) in the non-anemic group, an association that was highly statistically significant (P\u0026lt;0.001). This powerful correlation suggests that the development of anemia or the presence of anemia in CAP patients is not merely an epiphenomenon but a potent marker of critical illness and a strong independent predictor of fatal outcome\u003csup\u003e43,44\u003c/sup\u003e. The pathophysiological link may be explained by a severe systemic inflammatory response suppressing erythropoiesis and reducing iron availability\u003csup\u003e37\u003c/sup\u003e, coupled with a diminished oxygen-carrying capacity that exacerbates tissue hypoxia in vital organs\u003csup\u003e45\u003c/sup\u003e. This can precipitate multi-organ failure, which is a likely final common pathway for these patients. Our analysis revealed that the length of stay was markedly prolonged for patients who developed anemia, with a mean of 13.1 \u0026plusmn; 7.2 days, compared to only 5.4 \u0026plusmn; 2.1 days for those who did not (P\u0026lt;0.001). This more than twofold increase in hospitalization time is not only statistically robust but also carries substantial clinical and economic implications.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe Receiver Operating Characteristic (ROC) curve analysis presented in Figure 1 revealed an Area Under the Curve (AUC) of 0.64 (P=0.001) for hemoglobin as a predictor of disease severity. While statistically significant, an AUC of 0.64 suggests a modest predictive capability for hemoglobin alone. An AUC value of 0.7 is typically considered the minimum threshold for a \u0026apos;fair\u0026apos; predictor, indicating that hemoglobin, while informative, may not be a standalone, highly accurate indicator of CAP severity in this cohort. The optimal predictive threshold identified was a hemoglobin level of 10.25 g/dL. This value is particularly relevant as it falls within the standard definitions of anemia, reinforcing the clinical significance of anemia in stratifying patient risk. The modest predictive value underscores the complexity of CAP severity, which is influenced by multiple factors beyond a single hematological parameter.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable (2): Association of Anemia Status with Clinical Outcomes and Patient Demographics\u003c/strong\u003e\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"570\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 142px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eOutcome\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 159px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eAnemic patients (n=52)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 168px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eNon-anemic patients (n=8)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 101px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eP-value\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 142px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eLength of Hospital Stay (LOHS), days\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 159px;\"\u003e\n \u003cp\u003e13.1\u0026plusmn;7.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 168px;\"\u003e\n \u003cp\u003e5.4\u0026plusmn;2.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 101px;\"\u003e\n \u003cp\u003e\u0026lt;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 142px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eComplications, n (%)\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003eDeath\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 159px;\"\u003e\n \u003cp\u003e24 (46.2%)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e7 (13.5%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 168px;\"\u003e\n \u003cp\u003e1 (12.5%)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e0 (0%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 101px;\"\u003e\n \u003cp\u003e\u0026lt;0.04\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026lt;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 142px;\"\u003e\n \u003cp\u003e\u003cstrong\u003ePSI Class, n (%)\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eI\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eII\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eIII-V\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 159px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e7(13.5%)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e14 (26.9%)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e30 (57.7%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 168px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e7 (87.5%)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e1 (12.5%)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e0 (0%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 101px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026lt;0.0001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 142px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eGender, n (%)\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eMales\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eFemales\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 159px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e31 (59.6%)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e21 (40.4%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 168px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e4 (50%)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e4 (50%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 101px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e0.6\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eThe development of anemia during hospitalization for CAP was not found to be influenced by patient gender. Our analysis revealed that among the 52 anemic patients, 31(59.6%) were male and 21 (40.4%) were female. This distribution was not significantly different from the non-anemic group, which consisted of 4 males (50%) and 4 females (50%) (P=0.6). The lack of a statistically significant association indicates that male and female patients were equally susceptible to development anemia in the context of their pneumonic illness, in contrast to Reade study which demonstrate that female gender was a risk factor for developing anemia in CAP patients\u003csup\u003e39\u003c/sup\u003e. This finding suggests that the pathophysiological mechanisms driving anemia in CAP--such as inflammation, nutritional deficits, or other illness- related factors\u0026mdash;are likely operative across both genders and that the potent prognostic value of anemia for worse outcomes is applicable to all patients, irrespective of sex.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eLimitations:\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003eOur study has several limitations that warrant consideration. First, this single-center study with a relatively small sample size (n=60) may limit the generalizability of the findings and increase the risk of Type II errors for less common outcomes. Second, we could not determine the specific etiology of the anemia (e.g., iron deficiency versus anemia of chronic inflammation), which could affect the appropriate management strategy. Future studies should incorporate markers of iron status (ferritin, transferrin saturation) to better classify the type of anemia present. Finally, the inability to track post-discharge outcomes limits our understanding of long-term survival and readmission rates.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eAnemia is exceptionally common in hospitalized CAP patients and is strongly associated with longer hospitalization, higher complication rates, higher mortality rates, and higher disease severity scores (as measured by the Pneumonia Severity Index (PSI)). These findings demonstrate that anemia is not simply a comorbidity but rather a poor prognostic marker. The high prevalence of anemia among pneumonia patients in our study supports the idea that the body\u0026apos;s immune response to a pathogen decrease circulating iron, and the persistence of anemia after discharge reflects long-term mechanisms of iron retention as part of the immune response. Further research is warranted to assess whether aggressive management of anemia in this setting can improve clinical outcomes.\u0026nbsp;\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003eAI: Anemia of Inflammation\u003c/p\u003e\n\u003cp\u003eAUC: Area Under the Curve\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eBUN: Blood Urea Nitrogen\u003c/p\u003e\n\u003cp\u003eCAP: Community-Acquired Pneumonia\u003c/p\u003e\n\u003cp\u003eHgb: Hemoglobin\u003c/p\u003e\n\u003cp\u003ePSI: Pneumonia Severity Index\u003c/p\u003e\n\u003cp\u003eLMICs: Low- and Middle- Income Countries\u003c/p\u003e\n\u003cp\u003eLOHS: Length of Hospital Stay\u003c/p\u003e\n\u003cp\u003eROC: Receiver Operating Characteristic\u003c/p\u003e\n\u003cp\u003eWHO: World Health Organization\u003c/p\u003e"},{"header":"Declarations","content":"\u003cul\u003e\n \u003cli\u003e\u003cstrong\u003eEthics Approval and Consent to Participate:\u0026nbsp;\u003c/strong\u003eThe study protocol was approved by the Ethics Committee of Latakia University and Latakia University Hospital. The study was conducted in accordance with the Declaration of Helsinki. Written informed consent was obtained from all participants or their legally authorized representatives prior to enrollment.\u003c/li\u003e\n \u003cli\u003e\u003cstrong\u003eConsent for Publication:\u003c/strong\u003e Not applicable.\u003c/li\u003e\n \u003cli\u003e\u003cstrong\u003eAvailability of Data and Materials:\u0026nbsp;\u003c/strong\u003eAvailable from the corresponding author on reasonable request.\u003c/li\u003e\n \u003cli\u003e\u003cstrong\u003eCompeting Interest:\u003c/strong\u003e The authors declare that they have no competing interests.\u003c/li\u003e\n \u003cli\u003e\u003cstrong\u003eFunding:\u0026nbsp;\u003c/strong\u003eNo specific funding was received for this study.\u003c/li\u003e\n \u003cli\u003e\u003cstrong\u003eClinical Trial Registration:\u0026nbsp;\u003c/strong\u003eClinical trial number: not applicable.\u003c/li\u003e\n \u003cli\u003e\u003cstrong\u003eAuthors\u0026rsquo; Contributions:\u0026nbsp;\u003c/strong\u003eRwa Alzhraa Zreik contributed to the conceptualization, study design, and methodology. She was also responsible for drafting the main manuscript text (abstract, introduction, results, and discussion) and collaborated on the preparation and critical review of the study\u0026apos;s results, tables, and figures. Malek Hijazeah contributed to the conceptualization, study design, and methodology. Feras Hussein collaborated on the preparation and critical review of the study\u0026apos;s results, tables, and figures. All authors read and approved the final manuscript.\u003c/li\u003e\n \u003cli\u003e\u003cstrong\u003eAcknowledgements:\u0026nbsp;\u003c/strong\u003eNot applicable.\u003c/li\u003e\n\u003c/ul\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eIshiguro T, Takayanagi N, Yamaguchi S, et al. 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Anemia and Blood Transfusion in Critically Ill Patients. \u003cem\u003eJAMA\u003c/em\u003e. 2002;288(12):1499. doi:10.1001/jama.288.12.1499\u003c/li\u003e\n\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-pulmonary-medicine","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"pulm","sideBox":"Learn more about [BMC Pulmonary Medicine](http://bmcpulmmed.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/pulm/default.aspx","title":"BMC Pulmonary Medicine","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Community acquired pneumonia, anemia, mortality, prognosis","lastPublishedDoi":"10.21203/rs.3.rs-7957203/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7957203/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e \u003cp\u003edespite advances in diagnosis and antimicrobial therapy, community-acquired pneumonia (CAP) remains a significant cause of mortality. In critically ill hospitalized patients, mortality rates range from 5% to as high as 30\u0026ndash;50%. There is an increasing interest in studying the anemia prevalence among hospitalized patients and its consequences in comorbidity and mortality. Considering that CAP is the second leading cause of hospital admission, this study investigates the prevalence and progression of anemia in CAP patients, and its association with hospital stay, mortality, and pneumonia severity.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eThis prospective observational study analyzed 60 patients admitted to the hospital with CAP, classified according to the pneumonia severity index (PSI). Hemoglobin levels were measured on the day of admission, the fourth day, the seventh day, and at discharge. Anemia was categorized into five categories: no anemia, mild anemia (Hgb 12-10g/dl), moderate (Hgb 10-8g/dl), severe (Hgb 7.9-6.5g/dl), and life threatening (Hgb\u0026thinsp;\u0026lt;\u0026thinsp;6.5 g/dl). We examined the relationship between anemia and hospital stay duration, pneumonia severity, incidence of complication, mortality, and gender.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eAnemia was prevalent in 86.7% of patients hospitalized with CAP. Although our data did not show new development of anemia during hospitalization, the study found that anemia was associated with longer hospital stay, higher pneumonia severity, increased complications rate, and higher mortality rate of 11.9% overall.\u003c/p\u003e\u003ch2\u003eConclusion\u003c/h2\u003e \u003cp\u003eAnemia in CAP patients is not merely a comorbidity but is associated with poor prognosis and increased risk for complications and mortality.\u003c/p\u003e","manuscriptTitle":"The prevalence and development of anemia in community- acquired pneumonia patients and its association with the duration of hospitalization and mortality","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-12-30 09:35:53","doi":"10.21203/rs.3.rs-7957203/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewersInvited","content":"","date":"2025-12-24T10:53:58+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-12-22T22:04:15+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-12-01T20:40:10+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-12-01T19:39:53+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Pulmonary Medicine","date":"2025-12-01T19:33:58+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-pulmonary-medicine","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"pulm","sideBox":"Learn more about [BMC Pulmonary Medicine](http://bmcpulmmed.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/pulm/default.aspx","title":"BMC Pulmonary Medicine","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"1a96fa56-6d0f-44a0-9790-d5c5e24ad38e","owner":[],"postedDate":"December 30th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2025-12-30T09:35:53+00:00","versionOfRecord":[],"versionCreatedAt":"2025-12-30 09:35:53","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7957203","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7957203","identity":"rs-7957203","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}