Role of neutrophil lymphocyte ratio as a prognostic biomarker in COVID-19 infection in Indian patients: A single centre observational study from South India

Introduction: Early identification of severe disease in Coronavirus Disease-2019 (COVID-19) infection is important to reduce mortality and for the efficient allocation of medical resources. Several studies have established that severe cases of COVID-19 infections tend to have a higher Neutrophil Lymphocyte Ratio (NLR) and is an independent predictor of mortality. Aim: This study aimed to determine whether NLR can serve as a predictor of the prognosis of COVID-19 infections in Indian patients. Materials and Methods: This study was an ambispective observational single centre study conducted in Tirunelveli Medical College from March 2020 to July 2020. Clinical and laboratory data of 1100 laboratory-confirmed COVID-19 infected patients were reviewed in this study. The patients were categorised as, asymptomatic, mild, moderate, and severe cases based on their clinical presentation. The demographic, clinical characteristics and laboratory data on the day of admission were analysed and compared by tertiles of the NLR. The receiver operating curve was applied to determine the threshold of NLR and the prognostic value was assessed via the Kaplan-Meier curve and regression models. Results: A total of 1100 cases were included in the study and were subdivided based on the clinical presentation into mild (n=226), moderate (n=27), severe (n=67), and asymptomatic (n=780) cases. The overall mortality rate was 4.9%. The ROC curve indicated that NLR is a better predictor of severe disease than other haematological parameters, with 89.3% Area Under the Curve (AUC) at the cut-off value of 2.81 with 80.6% sensitivity and 87.1% specificity. Multivariate analysis established that patients with NLR >2.8 had higher odds (OR=19.809, 95% CI-10.159-38.622) of severe infection and mortality (HR=1.110, 95% CI-1.088-1.113). Kaplan-Meier curve showed a significant difference (p-value 2.8 (13.1 days). Conclusion: Early identification of COVID-19 patients with severe disease is important to reduce mortality. Elevated NLR is associated with severe disease in Severe Acute Resiratory Syndrome Coronavirus-2 (SARS-CoV-2) infection. NLR >2.8 in Indian population, may aid in identification of severe illness necessitating early access to intensive care unit and requirement of respiratory support.