Mean platelet volume can estimate the current vasculitis activity of microscopic polyangiitis

Mean platelet volume (MPV) was known to be associated with the inflammatory burdens in various diseases, but not microscopic polyangiitis (MPA) yet. In this study, we investigated the association between MPV and Birmingham vasculitis activity score (BVAS) in 88 patients with MPA. We retrospectively reviewed the medical records of 88 patients with MPA. Clinical and laboratory data at diagnosis and partially at follow-up were collected. Linear regression analyses were used to clarify the association between MPV and BVAS. We also stratified MPA patients into three groups according to tertile of BVAS and define the lower limit of the highest tertile as the cut-off of BVAS for severe MPA. The area under the receiver operator characteristic curve (AUROC) was used to identify the cut-off of MPV for severe MPA (8.85 fL). The mean age was 60.5 years and 25 patients were male (28.4%). In univariable linear regression analysis, MPV was negatively correlated with BVAS (r = -0.326). In multivariable linear regression analysis, MPA was independently associated with BVAS (beta = -0.260). When we classified MPA patients into two groups based on the cutoff of MPV for severe MPA, patients having MPV <= 8.85 fL exhibited the higher frequency of severe MPA than those having MPV > 8.85 fL (RR 5.000). In addition, MPV increased along with improvement of vasculitis activity during the follow-up. In conclusion, MPV is significantly associated with BVAS and it can estimate the current BVAS in patients with MPA.