Evaluation of hematological parameters as biomarkers of disease activity in drug-naïve patients with rheumatoid arthritis: a retrospective analysis

Background: Inflammatory processes play a central role in rheumatoid arthritis (RA), involving complex interactions among cytokines and blood cell components. Current clinical tools, including the Disease Activity Score (DAS28), and biomarkers such as erythrocyte sedimentation rate and C-reactive protein (CRP), have limitations in monitoring disease activity. Objectives: This study aimed to assess the utility of routine hematological parameters as potential biomarkers for diagnosing RA and evaluating disease activity in drug-naïve patients. Methods: In this single-center retrospective study, 486 RA patients and 301 age- and sex-matched healthy controls were analyzed. Drug-naïve RA patients (not treated with disease-modifying antirheumatic drugs or glucocorticoids) were selected according to the 2010 American College of Rheumatology/European League Against Rheumatism criteria. Hematological parameters (white blood cell count and differential, hemoglobin (HGB), platelet count (PLT), neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), red cell distribution width (RDW), and mean platelet volume (MPV)) were obtained and calculated from complete blood counts. Disease activity was assessed using the 28-joint DAS28 with CRP. Diagnostic accuracy and association with disease activity were evaluated using receiver operating characteristic (ROC) analysis, correlation tests, and logistic regression. Results: Compared with controls, RA patients exhibited distinct hematological profiles, with significantly higher NLR, PLR, and RDW, and lower MPV (all p < 0.001). Multivariate logistic regression identified MPV (odds ratio (OR): 1.315, 95% confidence interval (CI): 1.085–1.594, p = 0.005) and age (OR: 0.984, 95% CI: 0.969–0.999, p = 0.038) as independent factors associated with moderate-to-high disease activity. MPV showed significant inverse correlations with DAS28-CRP ( r = −0.098, p = 0.031) and CRP ( r = −0.148, p = 0.001). ROC analysis demonstrated that NLR had a modest performance (area under the curve (AUC): 0.676) for distinguishing RA patients from controls, and its performance in differentiating disease activity levels was weak (AUC: 0.598). Conclusion: This study suggests that hematological indices, particularly NLR, PLR, and MPV, hold potential as supplementary biomarkers in RA, but not standalone diagnostic tools. MPV emerged as an independent marker associated with higher disease activity, yet its clinical significance requires further validation. These readily available parameters may be integrated as complementary components of a broader diagnostic and monitoring strategy.