Predicting Mortality in Microscopic Polyangiitis with Renal Involvement: A Survival Analysis Based on 64 Patients

Background: To determine predictors of survival in patients with microscopic polyangiitis (MPA). Methods: A cohort of 64 patients who met the Chapel Hill criteria for MPA with renal involvement participated in the study. All subjects received cytotoxic drugs. All of the diagnoses were biopsy proven. Results: We retrospectively studied 64 patients (median age, 59 years; male/female ratio, 1.6:1). The mean follow-up was 38 months; 34 (53.13%) patients died or acquired end-stage renal disease. According to univariate analysis, a preliminary prognostic value was attributed to serum creatinine (Scr) > 459 mu mol/L (p < 0.001); erythrocyte sedimentation rate (ESR) > 99 mm/h (p < 0.001); serum albumin < 30 g/L (p < 0.001); and hemoglobin < 84 g/L (p < 0.001). Logistic regression analysis showed that Scr level (beta = 1.02, p = 0.0002) and ESR (beta = 1.02, p 0.0002) at baseline were associated with poor prognosis, and Cox regression analysis further confirmed this result [Scr: beta = 1.004, 95% confidence interval (CI): 1.002-1.006, p < 0.001; ESR: beta = 1.018, 95% CI: 1.000-1.037, p = 0.046]. The receiver operating characteristic curve showed that Scr and ESR were predictors of MPA patient prognosis, their areas under the curves were 0.95 and 0.80, their sensitivities were 94.1% and 92.3%, and their specificities were 94% and 70%, respectively. Conclusion: Despite the small number of patients in this study, the prevalence of renal vasculitis was high in patients with MPA. The level of Scr and ESR may be a useful clinical biomarker for monitoring prognosis.