Evaluating the neutrophil-to-lymphocyte ratio as an indicator for early referral of patients with COVID-19 pneumonia to a high-care facility

Abstract

Background. Early identification of patients at high risk of severe disease requiring referral and treatment at a high‐care facility is imperative in the management of COVID‐19 pneumonia in a limited‐resource setting, as transfer of unstable patients can be detrimental. Objectives. To examine the value of the neutrophil‐to‐lymphocyte ratio (NLR) calculated on admission to a healthcare facility as a predictor of the need for early referral to a high‐care facility for further treatment. Methods. We designed a cohort analytical study of 198 patients with COVID‐19 pneumonia admitted to the COVID‐19 unit at Universitas Academic Hospital in Bloemfontein, South Africa, between 20 May and 30 September 2021. Results. Of the 198 patients enrolled in the study, 134 (67.7%) were admitted to high care and 93 (46.9%) died. The median (interquartile range (IQR)) NLR measured on admission to the hospital was 8.09 (4.90 ‐ 14.86), and the NLR ranged from 0.26 to 136.7. The admission NLR was statistically significantly higher in the high‐care group v. the general ward group (p<0.001). After converting the NLR to log scale, to bring it closer to conditional normality, logistic regression analysis identified log NLR (odds ratio (OR) 4.089; 95% confidence interval (CI) 2.464 ‐ 6.787; p<0.001) and age (OR 1.029; 95% CI 1.004 ‐ 1.056; p=0.024) as significant in determining who will require high care. The area under the receiver operating characteristic curve for the combined model of NLR and age was 0.829 (95% CI 0.767 ‐ 0.891). An NLR cut‐off value of 7.5 (sensitivity 0.7462, specificity 0.7968) has been calculated as the optimal cut‐off value to determine who will need high care. Admission log NLR and age were significant in determining who died (OR 2.067; 95% CI 1.404 ‐ 3.045; p<0.001, and OR 1.043; 95% CI 1.018 ‐ 1.068; p=0.001, respectively). Conclusion. The NLR measured on admission and age can be used to predict whether a patient with COVID‐19 pneumonia will require high care.