Role of neutrophil-to-lymphocyte ratio as a marker of acute exacerbation of chronic obstructive pulmonary disease

Abstract Background: Neutrophil-to-lymphocyte ratio (NLR) is as good as or better than C-reactive protein (CRP) as an indicator of acute exacerbation of chronic obstructive pulmonary disease (AECOPD). Moreover, there is no need of any special blood test as required for erythrocyte sedimentation rate (ESR) and CRP. It is cheaper, gives fast results, is easier, and is available everywhere. Objective: The objective of this study was to study the role of NLR as a marker of AECOPD. Materials and Methods: A prospective observational study was carried out among 140 study subjects. Among them, 70 were hospitalized for AECOPD. These cases were followed during the study period, and investigations were repeated after 3 months of stable chronic obstructive pulmonary disease (COPD). Another 70 age- and sex-matched healthy controls were included. Investigations such as spirometry, complete blood count, ESR, and CRP were done. Results: All groups were comparable for age and sex ( P > 0.05). Forced expiratory volume in 1 s (FEV 1 ), forced vital capacity (FVC), and FEV 1 /FVC ratio were significantly lower in the patients with AECOPD compared to stable COPD and healthy controls ( P < 0.05). NLR, CRP, and ESR were significantly higher in AECOPD compared to stable COPD and healthy controls ( P < 0.05). NLR was significantly correlated with FEV 1 , FVC, FEV 1 /FVC ratio, lymphocytes, hemoglobin, total leukocyte count, neutrophils, ESR, and CRP ( P < 0.05). The area under the curve was 0.975 (95% confidence interval = 0.953–0.998; P < 0.05). With a cutoff of 3.36, sensitivity was 92.9%, and specificity was 91.4%. With a cutoff of 3.36, only 5 (7.1%) of the 70 cases could be diagnosed as not having the AECOPD. Conclusion: NLR is as good as CRP as an inflammatory marker as it is highly correlated with it. NLR has a very good sensitivity and specificity as a marker of AECOPD using a cutoff value of 3.36.