International variation in the hospital burden of ANCA-associated vasculitis: a multinational ecological analysis, 2016-2022.

OBJECTIVES

To compare rates and characteristics of hospital episodes in which ANCA-associated vasculitis (AAV) was recorded as the primary discharge diagnosis across eight jurisdictions, including subtype distribution, demographic patterns, temporal trends, and in-hospital mortality.

METHODS

We conducted a multinational ecological cross-sectional study using national hospital discharge databases from eight jurisdictions (Spain, Australia, Germany, England, Wales, Chile, Mexico, and the USA) between 2016 and 2022. AAV episodes were identified using ICD-10 primary diagnosis codes for granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA), and eosinophilic granulomatosis with polyangiitis (EGPA). Crude and age-adjusted hospitalisation rates, hospitalisation rate ratios and in-hospital mortality were analysed. Temporal trends were primarily assessed using Pearson-scaled Poisson models, with negative binomial models as sensitivity analyses.

RESULTS

Among 758,257,987 hospital episodes, 116,039 were AAV (0.015%). GPA was the most frequent subtype (63.6%), followed by MPA (25.6%) and EGPA (10.9%). Crude AAV hospitalisation rates ranging from 0.04/100,000 in Mexico to 9.61/100,000 in Germany; age-adjusted rates were similar. Mortality data from Spain, Mexico, and the USA showed the highest AAV in-hospital mortality proportion in the USA (6.75%). In Pearson-scaled Poisson analyses, AAV hospitalisation rates increased in Spain (HRR 1.12, 95% CI 1.09-1.15; p < 0.001) and Australia (1.08, 1.06-1.10; p < 0.001), and decreased in Wales (0.86, 0.80-0.93; p < 0.001) and Chile (0.92, 0.86-0.98; p = 0.012). These trends persisted after exclusion of 2020 but were not statistically significant in negative binomial models.

CONCLUSIONS

AAV hospital burden varied substantially across jurisdictions in rates, subtype distribution, and outcomes, warranting cautious interpretation in light of differences in population structure and health system capture.