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

Background: We aimed to investigate the role of red blood cell distribution width (RDW)-to-platelet ratio (RPR) and mean platelet volume (MPV) in evaluating the disease activity of microscopic polyangiitis (MPA).

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 Activity Score (BVAS) was used to evaluate the disease activity.

Results: Compared with the healthy controls, RPR and RDW were significantly increased, and MPV was significantly decreased in MPA patients. In the MPA group, RPR was positively correlated with BVAS (p = 0.032), but negatively correlated with lymphocyte, hemoglobin, and complement 3 (all p < 0.05). MPV was negatively correlated with white blood cell (p = 0.045). Patients with BVAS > 15 had significantly 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% specificity in predicting MPA, and the combination of RPR and MPV had 75.3% sensitivity and 78.9% specificity in differentiating MPA patients from healthy controls.

Conclusions: The study suggests that RPR may be a potential marker of diagnosis and disease activity in newly diagnosed MPA patients. Additionally, a higher predictive value in monitoring and evaluation of MPA was found when RPR and MPV were combined.