Neutrophil-to-lymphocyte ratio as a predictor of clinical outcomes in critically ill COVID-19 patients: A retrospective observational study.

ABSTRACT

Background: Timely identification of patients at risk of worse clinical outcomes is vital in managing coronavirus disease 2019 (COVID-19). The neutrophil-to-lymphocyte ratio (NLR) calculated from complete blood count can predict the degree of systemic inflammation and guide therapy accordingly. Hence, we did a study to investigate the role of NLR value on intensive care unit (ICU) admission in predicting clinical outcomes of critically ill COVID-19 patients. Methods: We conducted a retrospective analysis of electronic health records of COVID-19 patients admitted to ICUs at Hazm Mebaireek General Hospital, Qatar, from March 7, 2020 to July 18, 2020. Patients with an NLR equal to or higher than the cut-off value derived from the receiver operating characteristic curve were compared to those with an NLR value below the cut-off. The primary outcome studied was all-cause ICU mortality. The secondary outcomes evaluated were the requirement of mechanical ventilation and ICU length of stay (LOS). Results: Five hundred and nineteen patients were admitted to ICUs with severe COVID-19 infection during the study period. Overall, ICU mortality in the study population was 14.6% (76/519). NLR on ICU admission of ≥6.55 was obtained using Youden's index to predict ICU mortality, with a sensitivity of 81% and specificity of 41%. Mortality was significantly higher in patients with age ≥60 years (p < 0.001), chronic kidney disease (p = 0.03), malignancy (p < 0.002), and NLR ≥ 6.55 (p < 0.003). There was also a significant association between the requirement of mechanical ventilation (34.7% vs. 51.8%, p < 0.001) and increased ICU LOS (8 vs. 10 days, p < 0.01) in patients with ICU admission NLR ≥ 6.55. Conclusion: Higher NLR values on ICU admission are associated with worse clinical outcomes in critically ill COVID-19 patients.