Prognostic value of neutrophil-to-lymphocyte ratio in COVID-19 compared with Influenza and respiratory syncytial virus infection

Abstract

A high neutrophil to lymphocyte ratio (NLR) is considered an unfavorable prognostic factor in various diseases, including COVID-19. The prognostic value of NLR in other respiratory viral infections, such as Influenza, has not hitherto been extensively studied. We aimed to compare the prognostic value of NLR in COVID-19, Influenza and Respiratory Syncytial Virus infection (RSV). A retrospective cohort of COVID-19, Influenza and RSV patients admitted to the Tel Aviv Medical Center from January 2010 to October 2020 was analyzed. Laboratory, demographic, and clinical parameters were collected. Two way analyses of variance (ANOVA) was used to compare the association between NLR values and poor outcomes among the three groups. ROC curve analyses for each virus was applied to test the discrimination ability of NLR. 722 COVID-19, 2213 influenza and 482 RSV patients were included. Above the age of 50, NLR at admission was significantly lower among COVID-19 patients (P < 0.001). NLR was associated with poor clinical outcome only in the COVID-19 group. ROC curve analysis was performed; the area under curve of poor outcomes for COVID-19 was 0.68, compared with 0.57 and 0.58 for Influenza and RSV respectively. In the COVID-19 group, multivariate logistic regression identified a high NLR (defined as a value above 6.82) to be a prognostic factor for poor clinical outcome, after adjusting for age, sex and Charlson comorbidity score (odds ratio of 2.9, P < 0.001). NLR at admission is lower and has more prognostic value in COVID-19 patients, when compared to Influenza and RSV.

Figure 1

NLR levels stratified by age groups. For each age group level of NLR was compared among COVID-19, Influenza and RSV patients. The average levels are displayed by mean and SD. NLR neutrophil-to-lymphocyte ratio, COVID-19 coronavirus disease 2019, RSV respiratory syncytial virus.

Figure 2

Two-way analysis of variance (ANOVA), using log-transformed NLR levels as the dependent variable, comparing the association between NLR values and adverse outcomes among COVID-19, Influenza and RSV patients. NLR neutrophil-to-lymphocyte ratio, COVID-19 coronavirus disease 2019, RSV respiratory syncytial virus.

Figure 3

Receiver operating characteristic (ROC) curves analyses for predicting poor outcomes for COVID-19, Influenza and RSV patients. NLR neutrophil-to-lymphocyte ratio, COVID-19 coronavirus disease 2019, RSV respiratory syncytial virus, AUC area under the curve.

Figure 4

Receiver operating characteristic (ROC) curve for logistic regression model used to test the discrimination ability of NLR (above or below 6.82) as a prognostic factor of poor clinical outcome adjusted to age, sex and Charlson comorbidity index among COVID-19 patients. NLR neutrophil-to-lymphocyte ratio, COVID-19 coronavirus disease 2019, AUC area under the curve, CCI Charlson comorbidity index.