The neutrophil-lymphocyte count ratio in patients with community-acquired pneumonia

Abstract

Study objective: The neutrophil-lymphocyte count ratio (NLCR) has been identified as a predictor of bacteremia in medical emergencies. The aim of this study was to investigate the value of the NLCR in patients with community-acquired pneumonia (CAP).

Methods and results: Consecutive adult patients were prospectively studied. Pneumonia severity (CURB-65 score), clinical characteristics, complications and outcomes were related to the NLCR and compared with C-reactive protein (CRP), neutrophil count, white blood cell (WBC) count. The study cohort consisted of 395 patients diagnosed with CAP. The mean age of the patients was 63.4 ± 16.0 years. 87.6% (346/395) of the patients required hospital admission, 7.8% (31/395) patients were admitted to the Intensive Care Unit (ICU) and 5.8% (23/395) patients of the study cohort died. The NLCR was increased in all patients, predicted adverse medical outcome and consistently increased as the CURB-65 score advanced. NLCR levels (mean ± SD) were significantly higher in non-survivors (23.3 ± 16.8) than in survivors (13.0 ± 11.4). The receiver-operating characteristic (ROC) curve for NLCR predicting mortality showed an area under the curve (AUC) of 0.701. This was better than the AUC for the neutrophil count, WBC count, lymphocyte count and CRP level (0.681, 0.672, 0.630 and 0.565, respectively).

Conclusion: Admission NLCR at the emergency department predicts severity and outcome of CAP with a higher prognostic accuracy as compared with traditional infection markers.

Figure 1. Admission levels of the neutrophil-lymphocyte count ratio, white blood cell count (×10e9/l) and C-reactive protein level (mg/l) in community-acquired pneumonia patients classified into five CURB-65 categories (0, 1, 2, 3 and 4+5), (NLCR, neutrophil-lymphocyte count ratio; WBC, white blood cell; Y-axis left CRP, C-reactive protein; Y-axis right) data are presented as mean and SD.

Figure 2. Receiver operating characteristic curves comparing C-reactive protein and the neutrophil-lymphocyte count ratio with respect to prediction of death (NLCR, neutrophil-lymphocyte count ratio; CRP, C-reactive protein).