Neutrophil-to-lymphocyte ratio as a serum biomarker associated with community acquired pneumonia

Community acquired pneumonia (CAP) is the main infectious cause of mortality in the world. Several scales evaluates outcomes, however the current tendency favors using biomarkers as surrogates of clinical prognosis.To evaluate utility of neutrophil-to-lymphocyte ratio to identify severe patients according to Pneumonia Severity Index scale.Observational and retrospective study in adults ≥18 years old with CAP, evaluated in an emergency ward of a secondary level hospital. Demography, laboratory results, treatment and Pneumonia Severity Index scale (PSI) data were collected. The neutrophil-to-lymphocyte ratio (NLR) between two groups was compared, high risk vs. low risk of complications according to PSI.94 patients were studied. There were not differences in tobacco smoking, comorbidities and outcomes between groups. Neutrophil total count, lymphopenia, and NLR were more elevated in the high risk group (p < 0.05). Uni and multivariate analysis showed that neutrophils and NLR could be surrogate of PSI III or higher (OR: 1.05 and 1.14 respectively). A NLR value ≥ 7.2 provided that probability (AUC 0.65; IC 95% 0.53-0.78).NLR is useful to identify patients with grave pneumonia and risk of complications according to PSI.