AB0381 VALIDATING DRAFT DCVAS CRITERIA IN A SINGLE CENTER GCA COHORT IN SOUTHERN NORWAY

Background: Giant cell arteritis (GCA) is the most common medium- and large vessel vasculitis in the elderly population. The diagnostic algorithm has changed in recent years in many institutions from temporal artery biopsy (TAB) to imaging based diagnosis (1). However, classification criteria that relied on TAB remained unchanged since 1990 (2). Reflecting the recent change in practice the Diagnostic and Classification Criteria for Vasculitis Study (DCVAS) group presented a draft classification criteria set for GCA. Endorsement by major scientific societies is currently pending (3). Objectives: To test the accordance of the GCA cohort of a single center in southern Norway between 2006 and 2018 to the draft DCVAS classification criteria in GCA. Methods: All patients diagnosed with GCA between 2006 and 2018 in our clinic were identified by international classification of disease (ICD) code for GCA (m31.5/m31.6) in the local electronic database. The draft DCVAS classification criteria were applied to all patients at the time of diagnosis, irrespective of the algorithm used to diagnose GCA. In the draft DCVAS classification criteria a score of 6 would be necessary to classify a patient as having GCA. Results: A total of 77 patients (55 female) diagnosed with GCA in the defined timespan were identified. Mean age was 69.2 years (57 – 83 years). As all patients were diagnosed with vasculitis and were older than 40 years of age, all patients met the compulsory criteria. The table 1 below shows the absolute number of patients that fulfilled the single criteria. The number of patients fulfilling the draft DCVAS classification criteria was 75 (97.4%). In the female cohort 96.4% patients finally diagnosed with GCA would be classified as having GCA as would 100% in the male cohort. Mean score was 12.4 (range 3-25). In 33.3 % of patients imaging was critical for classification. Laboratory findings were critical for classification in 9.3 %, head ache and scalp tenderness in 5.3%, temporal artery biopsy, morning stiffness and jaw claudication in 2.7%. The differentiation in possible and definite vasculitis in TAB did not change the result in any patient. Neither did sight-loss contribute to classify any patient. Five patients (6.5%) were diagnosed on clinical features and laboratory findings alone. Thirteen patients diagnosed with GCA and fulfilling DCVAS criteria had negative biopsies, three patients had an inconclusive TAB. Mean arterial biopsy length was 9 mm. Conclusion: A high percentage (97.4 %) of the patients diagnosed with GCA in our cohort fulfilled the draft DCVAS classification criteria. The high mean score (12.4) showed that DCVAS criteria did not depend heavily on single criteria. As diagnosis in our cohort was mainly based on ultrasound, imaging was the most critical item. This might be desirable as clinical features and laboratory markers should in general be confirmed by either imaging or TAB to ascertain diagnosis. However, five patients were solely diagnosed on clinical features and laboratory markers. Sight-loss did not contribute to classification in our cohort as most patients were seen in a fast-track clinic (FTC), but might be valuable in cohorts without FTC. References: [1]Dejaco C et al, Ann Rheum Dis. 2018;77(5):636-643 [2]Hunder GG et al, Arthritis Rheum. 1990 Aug;33(8):1122-8 [3]Merkel PA: oral presentation, American College of Rheumatology Annual Meeting 2018: October 19-24; 2018 Disclosure of Interests: None declared