Role of neutrophil-to-lymphocyte, lymphocyte-to-monocyte and platelet-to-lymphocyte ratios as predictors of disease severity in COVID-19 patients.

Direct viral damage and uncontrolled inflammation contribute to disease severity in SARS-CoV-2 infection. The aim of this study was to investigate the prognostic significance of neutrophil-to-lymphocyte [NLR], lymphocyte-to-monocyte [LMR] and platelet-to-lymphocyte [PLR] ratios in COVID-19 patients. All 184 COVID-19 patients hospitalized in our institution between March - April 2020 were retrospectively analyzed. The patients were grouped into intubated and non-intubated, and subgrouped into survived and deceased. An unpaired Student's t-test was used for continuous variables, and the Pearson Chi-square (χ2) test for categorical. Univariate and multivariate logistic regression models were developed to assess the independent relationship between NLR, LMR and PLR and unfavorable outcomes. Non-parametric correlations were calculated using Spearman's Rho correlation coefficient. The mean age of the patients was 64.7; mean BMI was 29.10; 73 (39.67%) were female and 111 male (60.33%). No statistical difference between groups was identified with regard to NLR (mean 8.29, standard deviation [SD] 7.86). On multivariate regression analysis, only PLR and LMR were shown to influence the ratio and it was positively correlated with PLR, lactate and C-reactive protein [CRP]. LMR for non-intubated survived [NI-S] (mean 2.29, SD 1.31) and non-intubated deceased [NI-D] (mean 1.79, SD 0.81) groups were statistically significant (p=0.03). LMR was influenced only by NLR on regression analysis. A positive correlation of LMR with body mass index [BMI] was ascertained. No statistical significance was found between groups for PLR (mean 269.85, SD 207.98) and the ratio was influenced by age and NLR on regression analysis, and positively correlated with NLR. To conclude, previously reported findings of a prognostic role of NLR, LMR and PLR in COVID-19 were not validated in our cohort and we would caution against using the ratios in question as independent markers for disease severity.