Prognostic utility of neutrophil-tolymphocyte ratio (NLR) in predicting outcomes among adults with communityacquired pneumonia: a systematic review and meta-analysis

<p>Community-acquired pneumonia (CAP) remains the primary cause of infectious mortality worldwide. Bedside severity scores (CURB-65 (confusion, urea, respiratory rate, blood pressure, age &ge;65) and the Pneumonia Severity Index [PSI]) provide static triage risk but lack dynamic sensitivity to progressive clinical deterioration. We synthesized evidence on the prognostic accuracy of the neutrophil-to-lymphocyte ratio (NLR) across adult CAP cohorts. Following Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 guidelines, four databases were searched for adult CAP cohorts reporting NLR-associated outcomes. Area under the curve (AUC) values were descriptively summarized across heterogeneous thresholds, and a random-effects meta-analysis of complete dichotomous mortality data was performed with pre-specified sensitivity analyses. A total of 19 adult cohorts (N = 19,188) were included. Across 14 studies reporting discriminative accuracy, NLR demonstrated moderate prognostic discrimination (descriptive mean AUC 0.736 &plusmn; 0.107, range 0.570-0.940). Across the 12 composite models, adding NLR yielded a descriptive mean AUC gain of +0.071, with a greater<br />enhancement for simpler bedside scores. Serial monitoring (days 3-5 vs. 1) distinguished survivors (declining NLR) from nonsurvivors (rising NLR). Across eight cohorts with dichotomous mortality data, elevated NLR was associated with increased mortality (random-effects risk ratio [RR] = 3.92, 95% confidence interval [CI]: 2.23-6.88; I&sup2; = 89.8%); sensitivity analysis excluding a zero-event outlier yielded RR = 3.48 (95% CI: 2.01-6.02; I&sup2; = 90.1%), while fixed-effect pooling yielded RR = 2.01 (95% CI: 1.78-2.28). NLR provides moderate prognostic discrimination in adult patients with CAP. Its principal clinical value is as an early serial marker and adjunctive<br />tool alongside CURB-65/PSI, not a standalone replacement.</p>