Neutrophil‐to‐monocyte ratio is the better new inflammatory marker associated with rheumatoid arthritis activity

BACKGROUND: Rheumatoid arthritis (RA) is a systemic autoimmune disease that chronically affects patients with episodes of inflammation. New inflammatory hematological markers were investigated for follow‐up, such as the neutrophil–monocyte ratio (NMR), lymphocyte monocyte ratio (LMR), and neutrophil–lymphocyte ratio (NLR). This study was conducted to determine the most useful marker based on studies of association with RA disease activity and correlation with the classical markers C‐reactive protein (CRP), erythrocyte sedimentation rate (ESR), and rheumatoid factor (RF). METHODS: This case‐control study included 62 chronic RA patients who had previously been diagnosed and experienced episodes of symptoms while attending a variety of public and private rheumatology clinics in Ibb City, Republic of Yemen, for the period of September 1 to November 30, 2021. Twenty healthy volunteers were included in this study. Complete blood count, CRP, ESR, and RF levels were measured in all participants. RESULTS: The total leukocyte count, neutrophil count, platelet count, NMR, LMR, and NLR were positively correlated with CRP and ESR, but the monocyte count was reversed. The area under the curve (AUC = 0.861, 95% confidence interval [CI] = 0.769–0.948) for the NMR cutoff value of 4.7 was equal to that of CRP and close to that of ESR. This NMR cutoff value had 87% sensitivity and 80% specificity. LMR and NLR cutoff values of 4.35 and 1.35, respectively, resulted in AUCs of (AUC = 0.807, 95% CI, 0.708–0.905) and (AUC = 0.699, 95% CI, 0.571–0.819); their sensitivity and specificity were 62.3%, 90%, 57.4%, and 80%, respectively. CONCLUSIONS: As a convenient and low‐cost inflammatory marker of RA activity, NMR outperformed LMR and NLR.