Background: Anti-neutrophil cytoplasmic antibodies (ANCA)-associated vasculitis (AAV) are included in the group of small vessel vasculitis. They are often associated with ANCA specificity for myeloperoxidase (ANCA-MPO) or proteinase 3 (PR3-ANCA) and include three clinical entities: granulomatosis with polyangiitis (GPA), eosinophilic granulomatosis with polyangiitis (EGPA) and microscopic polyangiitis (MPA). Their similarities in clinical features make the differential diagnosis a challenge for the physicians. In 1990 the American college of Rheumatology (ACR) developed classification criteria for AAV, including GPA and GEPA, but excluding MPA. In 2007 the European Medicine Agency (EMA) and in 2022 the ACR/EULAR) developed new classification criteria for the three subgroups of AAV (GPA, MPA and EGPA).

Objectives: To compare the three different classification criteria in AAV.

Methods: Study of patients diagnosed with AAV according to expert clinical rheumatologist opinion between January of 2000 and December of 2023 in a Northern Spanish region. Patients were reclassified based on the three set of criteria: ACR 1990, EMA 2007 algorithm and 2022 ACR/EULAR criteria. Patients not meeting the classification criteria were considered as undetermined vasculitis.

Results: We included 176 (92 men/84 women) patients; mean age at diagnosis of 69.5±13.6 years. According to expert rheumatologists, patients had been diagnosed as MPA (n=44; 25%) GPA (n=53; 30%), EGPA (n=23; 13 %) and undetermined AAV (n=56;32%).

With 1990 ACR criteria, 31(18%) patients were diagnosed with GPA, 14 (8%) patients were diagnosed with EGPA and 131 (74.4%) were classified like an indeterminate vasculitis. With the 2007 EMA algorithm 49 patients were diagnosis of GPA (28%) 16 (9%) with EGPA, 50 (28.4%) with MPA and 61(35%) like indeterminate. With the 2022 ACR/EULAR criteria, 67 (38 %) patients were diagnosed with MPA, 64 (36 %) with GPA, 24 (14 %) with EGPA and 21(12%) with undetermined AAV.

When the ACR 1990, EMA 2007 and the 2022 ACR/EULAR criteria were compared, we found that 2022 ACR/EULAR criteria were better to reclassify the undetermined AVV into the other three entities (Figure 1).

Conclusion: The ACR/EULAR 2022 showed the best correlation with the expert clinical rheumatologist opinion to classify AAV.

REFERENCES: [1] Kuwata R, Evaluation of the Validity of the 2022 American College of Rheumatology/European Alliance of Associations for Rheumatology Classification Criteria for Antineutrophil Cytoplasmic Antibody-associated Vasculitis for an Asian Population on the Basis of the Patterns of Organ Involvement [abstract]. Arthritis Rheumatol. 2023; 75 (suppl 9).

Figure 1.

Differences between expert clinical opinion (EXP), ACR 1990, EMA 2007 and ACR/EULAR 2022 criteria.

Acknowledgements: NIL.

Disclosure of Interests: Fabricio Benavides-Villanueva: None declared, Diana Prieto-Peña: None declared, Vanesa Calvo-Río: None declared, Ricardo Blanco Abbvie, Pfizer, Roche, Bristol-Myers-Squibb, Janssen, Lilly, Novartis, UCB and MSD., Abbvie, MSD and Roche.