The incidence, prevalence and mortality of granulomatosis with polyangiitis in the UK Clinical Practice Research Datalink

Objective. To estimate the incidence, prevalence and mortality of granulomatosis with polyangiitis in the UK. Methods. We conducted a historical cohort study using data from the Clinical Practice Research Datalink and Hospital Episode Statistics (HES). We calculated incidence rate ratios, adjusted for age, gender and ethnicity, using Poisson regression. Results. We identified 462 cases diagnosed between 1997 and 2013. Our overall estimate of incidence was 11.8 (95% CI: 10.7, 12.9)/million person-years. The incidence was 0.88 (95% CI: 0.40, 1.96) in children (aged<16 years) and 14.0 (95% CI: 12.8, 15.4) in adults. The incidence was lower in females (adjusted incidence rate ratio = 0.68; 95% CI: 0.56, 0.81) and highest in the 55-69 year age group (adjusted incidence rate ratio = 6.8, 95% CI: 4.9, 9.6; reference group 16-39 years). The incidence was not significantly different in the Black/Minority Ethnic population from that in theWhite population (adjusted odds ratio = 0.78, 95% CI: 0.53, 1.13, P= 0.13). The prevalence in 2013 was 134.9 (95%CI: 121.3, 149.6)/million. Mortalitywas 13.6% at 1-year, and higher in theHES- than in theClinical Practice Research Datalink-identified cases (hazard ratio = 3.16, 95% CI: 2.19, 4.56, P<0.001). Conclusion. By combining primary and secondary care datasets, we have found the incidence and mortality of granulomatosis with polyangiitis to be higher than previously reported. We predict that at present each year in the UK there will be -700 new cases, of whom 95 will die within 12 months.