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

Abstract

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. 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. 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. 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). The NLR measured on admission and age can be used to predict whether a patient with COVID-19 pneumonia will require high care.