Ab1327 Validation of the 2022 Acr/Eular Classification Criteria for Large-Vessel Vasculitis; Confusion of Classification Between Certain Ages Remains

Background: Takayasu arteritis (TA) and Giant cell arteritis (GCA) are classified as large vessel vasculitis (LVV). Both diseases have common clinical manifestations and no specific diagnostic tests. Differentiation of the two diseases is important because of differences in therapeutic approach. 2022 ACR/ EULAR classification criteria for LVV have been presented [1,2]. Objectives: we aimed to evaluate the diagnostic performance of new criterias in LVV patients compared to the old ones and to describe the characteristics of patients who met both criteria, with and without regard the age criteria. Methods: In this retrospective cross-sectional study, medical records of patients diagnosed with TA and GCA at the Rheumatology Clinic of Ankara Bilkent City Hospital were reviewed. The study included 54 patients with a clinical diagnosis of TA and 31 patients with a clinical diagnosis of GCA. Patients with GCA were used as controls to assess TA criteria and vice versa. Each patient with TA or GCA was assessed to determine whether they met the 1990 ACR classification criteria and the 2022 ACR/EULAR classification criteria. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), likelihood ratio of a positive test (LR+) or negative test (LR-), and inter-rater reliability of each classification criterion were assessed using standard formulas to compare the 1990 ACR and 2022 ACR/EULAR criteria for each diagnosis. Patients were analysed both with and without regard to age at diagnosis to assess the importance of age criteria. Statistical analyses and data visualization were performed with Jamovi (v2.3.22, Sydney, Australia). Results: Of the 54 patients with a clinical diagnosis of TA, 34 (63%) met the 1990 ACR classification criteria and 50 (92.6%) met the 2022 ACR/EULAR classification criteria. Of the 31 patients clinically diagnosed with GCA, 20 (65%) met the 1990 ACR classification criteria for GCA and 25 (81%) met the 2022 ACR/EULAR classification criteria for GCA. The revised criterias were more sensitive than the ACR criteria in diagnosing TA (92.6% vs. 63%) and GCA (80.6% vs. 64.5%). However, specificity of old criterias outperfom new ones for both TA (100% vs 93.5%) and GCA (100% vs 94.4). One patient with TA and one patient with GCA met both the 2022 ACR/EULAR classification criteria for TA and GCA. Where the age criterion is not considered, 5 (9.3%) TA patients and 3 (9.7%) GCA patients met both criteria. Conclusion: The 2022 ACR/EULAR criteria mark a significant advancement in the classification of LVV, reflecting modern clinical practice and the heterogeneity of vascular involvement. New criterias seem to have achieved their purpose in the classification of large vessel vasculitis with their increased sensitivity and better agreement with clinical diagnosis. We also found the age criterion to be an overly important factor for classifying LVV patients with its direct effect on the classification of 6 out of 8 patients. However, two patients who were in the common zone of the age entry criterion of both sets, meet both criteria. New criterias still do not seem to fully resolve the confusion of diagnosis between certain ages. Clinician opinion remains important for patients meeting both criteria, for early diagnosis and for the unclassifiable group of patients. Table 1. Clinical and laboratory characteristics of patients REFERENCES: [1] Grayson PC, Ponte C, Suppiah R, Robson JC, Gribbons KB, Judge A, et al. 2022 American College of Rheumatology/EULAR Classification Criteria for Takayasu Arteritis. Arthritis Rheumatol. 2022;74(12):1872-80. [2] Ponte C, Grayson PC, Robson JC, Suppiah R, Gribbons KB, Judge A, et al. 2022 American College of Rheumatology/EULAR classification criteria for giant cell arteritis. Ann Rheum Dis. 2022;81(12):1647-53. Acknowledgements: NIL. Disclosure of Interests: None declared.