Assessing pneumonia severity using neutrophil-to-lymphocyte and platelet-to-lymphocyte ratios: a cross-sectional comparison with CURB-65 score

Background: Community-acquired pneumonia continues to be a leading cause of morbidity and mortality worldwide. Several validated scoring systems are available for stratifying pneumonia severity, with the CURB-65 being well known. Recently, neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR) have been reported as reliable indicators of disease severity and adverse outcomes in patients with pneumonia, particularly when used alongside established scoring systems. Objectives: To evaluate the association of NLR and PLR with higher clinical severity classification (CURB-65 ⩾ 3), and to compare their discriminatory performance with C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) in patients with community-acquired pneumonia. Design: Cross-sectional study. Methods: In this cross-sectional study conducted at a tertiary care hospital in Peshawar, Pakistan, we enrolled 121 adults with community-acquired pneumonia. Baseline demographic characteristics, comorbid conditions, clinical presentation, and laboratory measures were recorded. Pneumonia severity was assessed using the CURB-65 score. The discriminatory performance of NLR, PLR, CRP, and ESR was evaluated by receiver operating characteristic (ROC) curve analysis, with severe pneumonia defined as a CURB-65 score of 3 or higher. Multivariable logistic regression was performed to assess independent associations after adjustment for age and comorbidities. Results: The mean (±SD) age of the patients was 59.2 ± 20.6 years, and 69.4% were male. Common comorbidities included diabetes (31.4%), chronic obstructive pulmonary disease (28.1%), and chronic heart failure (19.8%). The mean CURB-65 score was 2.23 ± 1.20. NLR and PLR were significantly higher in severe pneumonia than in non-severe pneumonia (both p < 0.001), whereas CRP and ESR did not differ significantly ( p = 0.083 and p = 0.197, respectively). In multivariable analysis, NLR remained independently associated with severe pneumonia (adjusted OR 1.91, 95% CI 1.46–2.51; p < 0.001). In ROC analysis, PLR showed the highest discriminative ability (area under the curve (AUC) 0.9935, 95% CI 0.9847–1.0000), followed by NLR (AUC 0.9436, 95% CI 0.8977–0.9895), CRP (AUC 0.6028, 95% CI 0.4878–0.7178), and ESR (AUC 0.5501, 95% CI 0.4258–0.6744). Conclusion: In this cohort, NLR and PLR demonstrated strong agreement with higher CURB-65 severity classification and superior discriminatory performance compared with CRP and ESR.