Improved outcome in Wegener's granulomatosis and microscopic polyangiitis? A retrospective analysis of 95 cases in two cohorts

Mortality rates for Wegener's granulomatosis (WG) and microscopic polyangiitis (MPA) have decreased after the introduction of cyclophosphamide. Standardized mortality ratio (SMR) expresses the overall mortality of patients compared with the general population. The aims of this study were to compare survival in an old and a recent cohort of patients with WG and MPA using SMR and to determine predictors for death in both groups combined. Survival analyses were performed by Kaplan-Meier survival curves, SMR and proportional hazards regression models. The nephrology and rheumatology clinics at Linkoping University Hospital, Sweden. All patients diagnosed with WG or MPA in the catchment area during 1978-2005 were divided into two cohorts; patients diagnosed before (n = 32, old cohort) and after (n = 63, recent cohort) December 31, 1996. The two cohorts differed regarding the proportion of WG (75% vs. 56%, P = 0.03) and a tendency for more pronounced kidney involvement in the old cohort: 266 mu mol L(-1) (16% dialysis-dependent) vs. 192 mu mol L(-1) (5% dialysis-dependent), but were comparable regarding disease severity. SMR at 1 and 5 years were 2.1 (95% CI: 0.43-6.09) and 1.6 (95% CI: 0.6-3.2) in the recent cohort and 5.2 (95% CI: 1.07-15.14) and 2.5 (95% CI: 0.93-5.52) in the old cohort. Five-year survival was 87% and 81%. Serum creatinine, age, end-stage renal disease, diagnosis before 1997 and first relapse were independent predictors for death. Patient survival in WG and MPA analysed with SMR may be better than previously believed. Severe renal disease and disease relapse were the major predictors of reduced survival.