Exploratory evaluation of the complete blood count-derived hematologic indices for diagnostic discrimination of rheumatoid arthritis and their relationship with disease activity: a cross-sectional study

Abstract

Background. Hematologic indices derived from the complete blood count (CBC) have attracted interest as potential inflammatory biomarkers in rheumatoid arthritis (RA). These indices include red cell distribution width (RDW), mean platelet volume (MPV), and platelet distribution width (PDW). The aim of this study was to evaluate the diagnostic discrimination of individual, dual, and composite hematologic indices for distinguishing RA patients from healthy controls and to assess their correlations with disease activity. Methods. This cross-sectional study included 51 RA patients and 51 matched healthy controls. Standardized z-scores were used to construct dual and composite indices. Diagnostic accuracy was assessed using receiver operating characteristic (ROC) analysis, and logistic regression models were used to estimate predictive values. Disease activity was measured by the Disease Activity Score-28 (DAS28-ESR). Results. MPV had an area under the curve (AUC) of 0.817 (95% confidence interval [CI]: 0.730–0.892), while PDW had an AUC of 0.762 (95% CI: 0.666–0.842). The dual index MPV + PDW yielded an AUC of 0.830, while the composite index had an AUC of 0.816 (95% CI: 0.720–0.895), with a specificity of 100%. The dual index RDW + PDW correlated significantly with DAS28-ESR (Spearman’s r = 0.316, p = 0.024). Conclusion. The combined MPV and PDW score showed promising diagnostic discrimination for RA, while the combined RDW and PDW score showed a significant correlation with disease activity. These findings require further validation.