POS1174 IMPACT OF THE 2022 ACR/EULAR CLASSIFICATION CRITERIA ON CLINICAL DIAGNOSIS OF ANTINEUTROPHIL CYTOPLASMIC ANTIBODY (ANCA) ASSOCIATED VASCULITIS

Abstract

BackgroundIn 2022 the American College of Rheumatology (ACR) and European Alliance of Associations for Rheumatology (EULAR) presented new classification criteria for the three subsets of antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV): granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA) and Eosinophilic Granulomatosis with Polyangiitis (EGPA).[1-3]The purpose of this classification was to ensure homogeneous populations for clinical trials and research. These criteria were developed based on a population of patients with a high certainty of diagnosis.[1-3]As with any novel criteria, these can potentially lead to re-classification of AAV patients which can impact selection of patients in future studies.ObjectivesTo assess the impact of the new 2022 ACR/EULAR classification criteria for GPA, MPA and EGPA on re-classification of clinical diagnoses of AAV patients.MethodsAn established cohort of 337 patients of AAV patients at a single center, academic hospital was used to screen patient and disease characteristics and clinical data at the time of diagnosis and matched to the novel 2022 ACR/EULAR classification criteria for GPA, MPA or EGPA. Patients with an unspecified AAV diagnosis and patients with no clinical data or only ANCA serology available for the time of diagnosis were excluded.ResultsIn total 249 patients, 160 (64%) and 89 (36%) females, with a median age of 66 (range 12-96) and a AAV diagnosis between 1983 to 2022, were included. 179 patients had a clinical diagnosis of GPA, 43 of MPA and 27 of EGPA.Of the 179 GPA patients, 155 (87%) met the classification criteria for GPA, 15 (8%) for MPA and 10 (6%) remained unclassified. One patient could be classified as both GPA and MPA. Of the 43 MPA patients, 33 (77%) classified as MPA, 8 (19%) as GPA and 3 (7%) patients remained unclassified. Again, one patient could be classified as GPA and MPA. Only 14 of 27 (52%) EGPA patients met the classification criteria for EGPA. Three (11%) EGPA patients classified as GPA, 4 (15%) as MPA and 6 (22%) remained unclassified. These results show a lower sensitivity than observed in the development study (87 vs 93% for GPA, 78 vs 93% for MPA and 52 vs 85% for EGPA).[1-3]When analysing our cohort based on ANCA specificity, from 67 MPO positive patients, 50 (75%) would classify as MPA, 9 (13%) as GPA and 4 (6%) as EGPA. Clinical diagnosis was MPA in only 40 (60%) of patients and GPA in 18 (27%) patients and EGPA in 9 (13%) patients. From 145 PR3 positive patients, 141 (97%) would classify as GPA, none as MPA and 1 (1%) as EGPA, compared to 140 (97%) clinical diagnosis of GPA, 1 (1%) of MPA and 4 (3%) of EGPA.ConclusionWhen comparing the EULAR/ACR classification criteria to real-life clinical diagnosis, 13% of GPA patients, 23% MPA patients and 48% of EGPA patients would not meet the criteria for the corresponding classification. Moreover, because the presence of ANCA auto-antibodies is highly weighted, the percentage of MPO positive GPA patients is diminished.We demonstrate using these new criteria will impact selection of patients in future studies, especially for EGPA studies.