Association of White Blood Cell Count, Neutrophil-to-Lymphocyte Ratio, and Procalcitonin with Severe Community-Acquired Pneumonia: Experience form a Tertiary Care Hospital

Abstract

Background:Community-acquired pneumonia (CAP) remains a leading cause of hospitalization and mortality worldwide. Early recognition of severe cases is essential for timely intervention, yet traditional severity scores have limitations. Readily available biomarkers such as white blood cell (WBC) count, neutrophil-to-lymphocyte ratio (NLR), and procalcitonin (PCT) may aid in improving severity assessment. Objective: To determine the relationship between white blood cell (WBC), neutrophil-to-lymphocyte ratio (NLR), procalcitonin (PCT), and severe Community Acquired Pneumonia. Methodology:This cross-sectional study was conducted at a tertiary care hospital and included 260 adult patients diagnosed with CAP based on clinical features and chest radiographic findings. Patients with hospital-acquired pneumonia, immunosuppression, hematologic disorders, or incomplete records were excluded. Severity of CAP was categorized as severe or non-severe according to ATS/IDSA criteria. Statistical analysis was performed using SPSS version 26.0. Group comparisons were made using chi-square, t-test, or Mann–Whitney U test. Logistic regression was used to identify independent predictors, and ROC curve analysis evaluated the discriminative power of biomarkers. Results:The mean WBC count (14.2 ± 4.7 vs. 9.6 ± 3.5 ×10?/L), NLR (10.8 ± 5.2 vs. 5.7 ± 3.1), and PCT (3.2 ± 1.8 vs. 0.9 ± 0.6 ng/mL) were significantly higher in severe CAP compared to non-severe cases (p<0.001 for all). ROC analysis showed PCT had the highest predictive ability (AUC 0.86), followed by NLR (AUC 0.81) and WBC (AUC 0.69). Conclusion:Elevated WBC, NLR, and PCT levels are strongly associated with severe CAP, with PCT demonstrating the best predictive performance. These biomarkers can complement clinical scores for early risk stratification.