Role of NLR, PLR, ELR and CLR in differentiating COVID-19 patients with and without pneumonia

Objectives Neutrophil/lymphocyte ratio (NLR), platelet/lymphocyte ratio (PLR), monocyte/lymphocyte ratio (MLR), eosinophil/lymphocyte ratio (ELR), and C-reactive protein (CRP)/lymphocyte ratio (CLR) are well-established inflammatory indices. This study aimed to examine whether NLR, PLR, MLR, ELR and CLR could differentiate coronavirus disease 2019 (COVID-19) patients with pneumonia from those of without. Methods We retrospectively examined the laboratory parameters including CRP, D-dimer, procalcitonin and complete blood count of 306 COVID-19 patients (pneumonic = 152 and non-pneumonic = 154). NLR, PLR, MLR, ELR and CLR values of each patient were calculated. The ability of these indices to distinguish COVID-19 patients with and without pneumonia was determined by receiver operating characteristic (ROC) analysis. Results NLR, PLR and CLR values were higher while ELR value was lower in pneumonic COVID-19 patients compared with patients with non-pneumonic COVID-19 infection. MLR value was similar in the two groups. NLR, PLR and CLR were positively correlated with CRP and procalcitonin. ELR was negatively correlated with CRP. The ROC analysis revealed that the optimal cut-off value of CLR for discriminating COVID-19 patients with pneumonia from those without pneumonia was 1.14 and the area under curve (AUC) for CLR was 0.731 (sensitivity = 81.5% and specificity = 55.6%), which was markedly higher than the AUCs of NLR (0.622), PLR (0.585) and ELR (0.613). However, no statistical differences were observed between AUC values of NLR, PLR and ELR (P > .05). Conclusion Our findings showed that NLR, PLR, ELR and CLR indices can be used in differentiating COVID-19 patients with or without pneumonia. Among them, the CLR index was the best predictor of pneumonia in COVID-19 patients.