Abstract Objectives To clarify the differences in clinical phenotypes, therapeutic patterns, and outcomes of patients with granulomatosis with polyangiitis (GPA) and microscopic polyangiitis (MPA) across geographic regions using a multinational cohort. Methods Data were collected from patients with newly diagnosed or relapsing GPA or MPA in Europe, Japan and the USA from January to July 2020. The composite outcome of kidney failure and/or death within 52 weeks after treatment was evaluated, and the hazard ratios across the regions were estimated using the Cox proportional hazard model. Heterogeneities of the effects were investigated via thorough subgroup analyses. Results Among the 254 eligible patients (Europe, 137; Japan, 73; USA, 44), those in Japan were older and had higher proportions of MPO-ANCA positivity and lung involvement compared with Europe and the USA. The estimated glomerular filtration rate at diagnosis varied across regions, with the highest dialysis requirement in the USA. Cyclophosphamide and rituximab use were, respectively, 57% and 63% in Europe, 29% and 40% in Japan, and 34% and 86% in the USA. Within 52 weeks, 8%, 10% and 18% developed kidney failure, while 9%, 7% and 7% died in Europe, Japan, and the USA, respectively; and the composite outcome occurred in 15%, 14% and 23% of patients. The hazard ratios for kidney failure and/or death were comparable across regions; however, they varied among certain subgroups. Conclusions Although the kidney failure-free survival was comparable across continents, regional differences existed in clinical phenotypes and therapeutic patterns.

Differences in phenotypes, treatments, and outcomes of ANCA-associated vasculitis across Europe, Japan and the USA in 2020