Predictive role of red blood cell distribution width to platelet ratio combined mean platelet volume in patients with microscopic polyangiitis

Background: We aimed to in-vestigate the role of red blood cell distribu-tion width (RDW)-to-platelet ratio (RPR) and mean platelet volume (MPV) in evaluating the disease activity of microscopic polyan-giitis (MPA). Materials and methods: A total of 73 newly diagnosed MPA patients and 57 healthy controls were enrolled in this study. The hematologic and biochemical indexes of two groups were assessed. The RPR was calculated as the ratio of RDW and platelet counts, and Birmingham Vasculitis Activ-ity Score (BVAS) was used to evaluate the disease activity. Results: Compared with the healthy controls, RPR and RDW were significantly increased, and MPV was sig-nificantly decreased in MPA patients. In the MPA group, RPR was positively correlated with BVAS (p = 0.032), but negatively cor-related with lymphocyte, hemoglobin, and complement 3 (all p < 0.05). MPV was nega-tively correlated with white blood cell (p = 0.045). Patients with BVAS > 15 had signifi-cantly higher RPR than patients with BVAS <= 15 (p = 0.011). A cut-off level of 0.066 for RPR had 47.9% sensitivity and 90.4% speci-ficity in predicting MPA, and the combina-tion of RPR and MPV had 75.3% sensitivity and 78.9% specificity in differentiating MPA patients from healthy controls. Conclusion: The study suggests that RPR may be a poten-tial marker of diagnosis and disease activity in newly diagnosed MPA patients. Addition-ally, a higher predictive value in monitoring and evaluation of MPA was found when RPR and MPV were combined.