ASSOCIATION OF NEUTROPHIL-TO-LYMPHOCYTE RATIO, C REACTIVE PROTEIN, AND LACTATE DEHYDROGENASE WITH DISEASE SEVERITY IN COMMUNITY-ACQUIRED PNEUMONIA: A CROSS-SECTIONAL STUDY

Abstract

Background: Community-acquired pneumonia (CAP) remains a major cause of infectious morbidity and mortality worldwide despite advances in antimicrobial therapy and supportive care. Early identification of patients at risk of severe disease is essential for appropriate triage and timely management. Although clinical severity scores such as CURB-65 and the Pneumonia Severity Index (PSI) are widely used, readily available inflammatory biomarkers may further improve early risk stratification. Methods: A hospital-based cross-sectional analytical study was conducted among 100 adult patients with community acquired pneumonia admitted to a tertiary care hospital. Demographic characteristics, clinical presentation, laboratory investigations, and chest radiographic findings were recorded. Neutrophil-to-lymphocyte ratio (NLR), C-reactive protein (CRP), and lactate dehydrogenase (LDH) levels were measured at admission. Disease severity was assessed using CURB-65 and PSI scores. Correlation analysis, multivariate logistic regression, and receiver operating characteristic (ROC) curve analysis were performed to evaluate the association and predictive performance of the biomarkers. Results: Among the 100 patients, 62% were males and the majority belonged to the 41–60-year age group (44%). Fever (92%), cough (88%), and dyspnoea (74%) were the predominant presenting symptoms. Mean NLR increased significantly from 4.2 ± 1.3 in mild CAP to 13.6 ± 3.1 in severe CAP (p<0.001). Similarly, CRP increased from 32.8 ± 18.5 mg/L to 142.7 ± 44.8 mg/L, while LDH increased from 278 ± 71 U/L to 604 ± 102 U/L across increasing severity categories (p<0.001 for both). NLR demonstrated the strongest correlation with CURB-65 (r=0.71), whereas CRP showed the highest correlation with PSI (r=0.74). Multivariate logistic regression identified NLR ≥10 (adjusted OR 4.82, p<0.001), CRP ≥100 mg/L (adjusted OR 3.42, p<0.001), LDH ≥450 U/L (adjusted OR 2.63, p=0.002), age >60 years, and diabetes mellitus as independent predictors of severe CAP. ROC analysis demonstrated excellent predictive performance for CRP (AUC 0.91), followed by NLR (AUC 0.89) and LDH (AUC 0.86). Conclusion: NLR, CRP, and LDH are inexpensive and readily available inflammatory biomarkers that show significant associations with disease severity and adverse clinical outcomes in community-acquired pneumonia. Their integration with established clinical severity scores may improve early identification of high-risk patients, facilitate prompt clinical decision-making, and optimize patient management, particularly in resource-limited settings.