The lymphocyte-monocyte ratio (LMR) is a systemic inflammatory marker for prediction of disease development, progress, and survival. Recently, a genome-wide association study identified genetic variations in ITGA4 and HLA-DRB1 that affect the LMR levels and were widely believed to be susceptibility genes for autoimmune diseases, including rheumatoid arthritis (RA). However, the role of LMR in RA patients remains unclear. The LMR level and other laboratory data of 66 RA patients, 163 osteoarthritis (OA) patients, and 131 healthy controls (HC) were compared using binary logistic regression. The correlations between LMR and disease activity and other inflammatory markers were measured using the Spearman rank test. ROC curve analyses assessed the diagnostic accuracy of LMR in RA. The LMR and lymphocyte count were significantly lower in RA patients, whereas the monocyte count was significantly higher relative to the HC group/OA patients (p < 0.01). A decreased LMR has been associated with increased disease activity (p = 0.012). In addition, the DAS28 and traditional inflammatory markers, including ESR, CRP, RDW, PLR, and NLR, and immune-related factors, such as C4, IgA, and IgM, were inversely correlated with LMR, while hemoglobin and albumin were positively correlated with LMR. The ROC curve showed that the area under the curve of LMR was 0.705 (95%CI = 0.630-0.781). The corresponding specificity and sensitivity were 82.82 and 45.45%, respectively. The present study shows that the LMR is an important inflammatory marker which could be used to identify disease activity in RA patients and to distinguish RA from OA patients.
Keywords: Disease Activity Score of 28 joints (DAS28); Disease activity; Inflammatory marker; Lymphocyte-monocyte ratio (LMR); Rheumatoid arthritis (RA).