Evaluation of Ministry of Health, Labour and Welfare diagnostic criteria for antineutrophil cytoplasmic antibody-associated vasculitis compared to ACR/EULAR 2022 classification criteria

Objective This study aimed to evaluate the Ministry of Health, Labour and Welfare (MHLW) diagnostic criteria for antineutrophil cytoplasmic antibody-associated vasculitis compared to the new American College of Rheumatology/European Alliance of Associations for Rheumatology 2022 criteria. Methods Two nationwide cohort studies were used, and participants were categorised as having eosinophilic granulomatosis with polyangiitis, granulomatosis with polyangiitis (GPA), or microscopic polyangiitis (MPA) according to the American College of Rheumatology/European Alliance of Associations for Rheumatology 2022 and MHLW criteria. Results Of the entire patient population, only 10 (2.1%) were unclassifiable according to the MHLW probable criteria, while a significant number of patients (71.3%) met at least two criteria. The MHLW probable criteria for MPA had some challenges in differentiating between MPA and eosinophilic granulomatosis with polyangiitis, and the same was true for MHLW probable criteria for GPA in differentiating MPA from GPA. Nevertheless, improved classification results were obtained when the MHLW probable criteria were applied in the order of eosinophilic granulomatosis with polyangiitis, MPA, and GPA. Conclusions The application of MHLW criteria could categorise a substantial number of patients with antineutrophil cytoplasmic antibody-associated vasculitis into one of the three antineutrophil cytoplasmic antibody-associated vasculitis diseases. The classification was in accordance with the American College of Rheumatology/European Alliance of Associations for Rheumatology 2022 criteria when considering the order of application.