Diagnostic accuracy of different blood cells-derived indexes in rheumatoid arthritis: A cross-sectional study

To evaluate the performance of different blood cells-derived indexes in the diagnosis of rheumatoid arthritis (RA). Neutrophil-to-lymphocyte ratio (NLR), lymphocyte to monocyte ratio, platelet to lymphocyte ratio (PLR), systemic inflammation response index (SIRI), and aggregate inflammation systemic index were calculated in 199 consecutive RA patients and 283 sex and age-matched controls (147 healthy donors and 136 patients with other rheumatic diseases). Area under the curve (AUCs), sensitivity and specificity were calculated to evaluate the accuracy of indexes in discriminating between RA and controls. Association between indexes and RA variables was explored by multiple linear regression analyses. Blood cells-derived indexes did not demonstrate good accuracy in differentiating RA from controls with lymphocyte to monocyte ratio, the index with the best diagnostic performance, having 63.6% of sensitivity and 65.3% specificity [AUC (95%CI) = 0.67 (0.62–0.72]. The accuracy of the indexes in differentiating RA from healthy donors was significantly higher than that (AUCs < 0.6 for all comparisons) differentiating RA from rheumatic diseases. In RA, SIRI and aggregate inflammation systemic index showed significant association with C-reactive protein and erythrocyte sedimentation rate. Our results do not support the use of blood cells-derived indexes for the diagnosis of RA, suggesting that they might reflect chronic inflammatory burden in rheumatic diseases rather than, specifically, in RA.