Platelet/Lymphocyte, Lymphocyte/Monocyte, and Neutrophil/Lymphocyte Ratios as Biomarkers in Patients with Rheumatoid Arthritis and Rheumatoid Arthritis-Associated Interstitial Lung Disease

BACKGROUND: The objective of this study was to assess the diagnostic value of platelet/lymphocyte ratio (PLR), lymphocyte/monocyte ratio (LMR), and neutrophil/lymphocyte ratio (NLR) as biomarkers in patients with rheumatoid arthritis (RA) and rheumatoid arthritis-associated interstitial lung disease (RA-ILD). MATERIAL/METHODS: Demographic and laboratory data were acquired for 198 RA and 103 RA-ILD patients and 290 healthy controls. The subjects were categorized into female and male groups and further subcategorized based on age into <60 years and ≥60 years subgroups. One-way analysis of variance (ANOVA), receiver operating characteristics (ROC), Pearson analysis, multiple linear regression analysis, and logistic regression analysis were performed to analyze the association of PLR, NLR, and LMR with RA and RA-ILD. RESULTS: Mean PLR and NLR were lowest in the control group, followed by the RA and RA-ILD groups (p<0.05). Mean LMR was lowest in the RA-ILD group, followed by the RA and control groups (p<0.05). The area under the ROC (AUROC) values of the PLR to distinguish between RA and controls, RA-ILD and controls, and RA-ILD and RA were 0.676, 0.776, and 0.650, respectively (p<0.001). Multiple linear regression analysis suggested a significantly positive association between the level of PLR and the level of DAS28 (p<0.001). The odds ratio of PLR was 1.101 for RA (p=0.023) and 1.217 for RA-ILD (p<0.001) when compared to the controls. CONCLUSIONS: PLR may be applied as a new biomarker for predicting and diagnosing RA and RA-ILD and for distinguishing RA-ILD patients from RA patients and healthy subjects.