Chest and renal involvements, Birmingham vascular activity score more than 13.5 and five factor score (1996) more than 1 at diagnosis are significant predictors of relapse of microscopic polyangiitis.

Objectives: We investigated whether specified organ involvements, antineutrophil cytoplasmic antibody (ANCA) positivity, Birmingham vasculitis activity score (BVAS) and five factor scores (FFS) at diagnosis could predict relapse of microscopic polyangiitis (MPA).

Methods: We reviewed the medical records of 90 patients with MPA. We collected clinical and prognostic data, (MPO)-ANCA and proteinase 3 (PR3)-ANCA, BVAS and FFS at diagnosis, and we compared them between the two groups. The optimal cut-off values of BVAS and FFS (1996) for predicting relapse were extrapolated.

Results: The mean age of patients (63 women) was 62.3 years and the mean follow-up duration was 41.7 months. At diagnosis, the mean BVAS, FFS (1996) and FFS (2009) of patients in no remission group were higher than those of patients in remission group (p<0.005 for all). Patients in relapse group exhibited chest and renal manifestations more frequently than those in no relapse group and the mean BVAS and FFS (1996) of patients in relapse group were significantly higher than those of patients in remission group (p<0.005 for all). There were no differences in MPO-ANCA and PR3-ANCA between the two groups. On multivariate logistic regression analysis, chest and renal manifestations were all independent predictors of relapse (OR 2.013 and OR 3.517). Patients who had BVAS ≥13.5 and FFS ≥ 1 exhibited a significantly increased risk of relapse than those who did not (RR 4.408 and RR 3.030).

Conclusions: Chest and renal involvements, BVAS ≥13.5 and FFS ≥1 at diagnosis were independent predictors of relapse of MPA.