Incidence and prevalence of granulomatosis with polyangiitis and microscopic polyangiitis in health management organization in Argentina: a 15-year study

Background/objective Our objective was to estimate incidence and prevalence rates of granulomatosis with polyangiitis (GPA) and microscopic polyangiitis (MPA) using data from a university hospital-based health management organization (HIMCO) in Latin America. Methods Multiple methods for case finding were used to ensure complete ascertainment. GPA was diagnosed if fulfilling ACR 1990 criteria or a clinical diagnosis was made by an experienced rheumatologist. For MPA, a clinical diagnosis made by an experienced rheumatologist in concordance with Chapel Hill 2012 consensus. Renal limited vasculitis (RLV) ANCA-P positive was considered along with MPA. Global, age-specific, and sex-specific incidence and prevalence rates were calculated for members of the HIMCO with continuous affiliation ≥ 1 year from January 2000 to January 2015. Each person was followed up until GPA or MPA were diagnosed, voluntarily withdraw of the HIMCO, death, or study finalization. Prevalence was calculated on January 1, 2015. Results Nineteen incident cases of GPA and 28 of MPA were identified from January 2000 to January 2015. During this period, a total of 349,775 HIMCO persons contributed a total of 2,073,438 person-years. GPA and MPA overall incidence rate per 1,000,000 person-years were 9 (95% CI 5–13) and 14 (95% CI 9–19), respectively. Age-specific incidence rates in both female and male patients peaked in the seventh decade of life in our population. On January 1, 2015, prevalence rates were 7.4 per 100,000 (95% CI 2.8–12) for GPA and 5.2 per 100,000 (95% CI 1.3–9) for MPA. Prevalence rates were higher in ages over 70 for both genders and both diseases. Conclusion In this first study from Latin America, incidence and prevalence rates were in ranges of previous reports from other sites of the world. In our population, GPA and MPA were more frequent in women and in older ages, and the incidence of MPA was higher than that of GPA. Key points • In Argentina, MPA incidence was higher than GPA, similar to that reported in other parts of the world . • Prevalence and incidence rates were higher in ages over 70 for both sexes and both diseases .