Predictive Value Of The Neutrophil-To-Lymphocyte Ratio For Disease Severity And Hospital Mortality In Patients With COVID-19: A Retrospective Cohort Study

Abstract

Background: Coronavirus disease 2019 (COVID-19) has an extended spectrum of disease severity, ranging from asymptomatic or mild infection to severe pneumonia, respiratory failure, multiorgan failure, and death. Early identification of patients at increased risk of clinical deterioration, severe or critical illness requiring intensive care unit (ICU) admission, and mechanical ventilation with prolonged hospital stay, as well as the potential increase of in-hospital mortality remains an integral part of Covid-19 patients' proper management. Neutrophil-to-lymphocyte ratio (NLR) reflects the balance between innate inflammatory response and adaptive immune suppression in Covid-19 patients. This study aimed to evaluate the predictive value of admission NLR for disease severity and mortality among hospitalized patients with COVID-19.

Methods: This retrospective cohort study included adult patients with laboratory-confirmed COVID-19 admitted to Zagazig University Hospitals from September 2021 till March 2022. Demographic characteristics, comorbidities, clinical findings, laboratory parameters, treatment characteristics, and outcomes were obtained from their medical records. NLR was calculated at hospital admission.

Results: A total of 389 patients were included. Severe/critical disease occurred in 48.1% of patients. The average age of severe cases was 52.3 ± 13.6 years, and 58% of them were male. At admission NLR was significantly higher in patients with severe/critical Covid-19.  After adjustment for age, sex, relevant comorbidities, high NLR remained independently associated with severe disease (OR 2.2; 95% CI:1.7 - 2.9; p < 0.001), and in-hospital mortality (OR 2.2; 95% CI:1.5 – 3.1; p < 0.001). Admission NLR cutoff 5.7 could predict the Covid-19 severity (AUC: 0.86, 95% CI: 0.82 – 0.89), and admission NLR cutoff 9.4 could predict the Covid-19 mortality risk (AUC: 0.91, 95% CI: 0.88 – 0.93).

Conclusions: A higher neutrophil-to-lymphocyte ratio at hospital admission was independently associated with severe COVID-19 and in-hospital mortality. Because NLR is inexpensive, rapidly available, and derived from a routinely performed complete blood count, it may provide a practical tool for early risk stratification. NLR should nevertheless be interpreted as part of a broader clinical assessment rather than as a stand-alone predictor.