Prevalence and incidence of Wegener's granulomatosis in the UK general practice research database

Abstract

Objective: Wegener's granulomatosis (WG) is a systemic vasculitis of unknown etiology. The UK General Practice Research Database (GPRD) contains the complete primary care records of approximately 3.6 million people. There are no data on the incidence and prevalence of WG from primary care. The aim of the study was to estimate the incidence and prevalence of WG in the GPRD population.

Methods: We identified all patients who had a first diagnosis of WG during 1990-2005, using Oxford Information System and Read codes. The diagnosis was verified by review of a randomly selected sample of 35 records that had identifying data removed. The annual incidence was calculated as the number of incident cases divided by the total person-years.

Results: A total of 295 patients (51.2% male) with a first diagnosis of WG were identified during 1990-2005. The median age was 59 years (interquartile range 47-70 years). The overall annual incidence of WG was 8.4 per million (95% confidence interval [95% CI] 7.5-9.4). The annual rate in women and men was 8.1 per million (95% CI 6.8-9.6), and 8.8 per million (95% CI 7.4-10.3), respectively. The incidence was stable throughout the study period. There was an increase in the annual prevalence from 28.8 per million in 1990 to 64.8 per million in 2005. The diagnosis was verified in 28 of 31 available case records.

Conclusion: This is the first study of the incidence and prevalence of WG in a database from a primary care population. The results are similar to previous studies from secondary and tertiary care and suggest that these studies are representative of the general population. The increasing prevalence with a constant incidence suggests that survival is improving with modern treatment protocols.