SAT0383 ENHANCED PERFORMANCE OF THE ASAS CLASSIFICATION CRITERIA BY DELETION OF NON-DISCRIMINATORY CLINICAL ITEMS: DATA FROM THE SCREENING IN AXIAL SPONDYLOARTHRITIS IN PSORIASIS, IRITIS, AND COLITIS COHORT
Authors: W. P. Maksymowych, R. Carmona, J. Chan, J. Yeung, S. Aydin, L. Martin, A. Masetto, O. Ziouzina, S. Keeling, S. Rohekar, R. Dadashova, J. Paschke, A. Carapellucci, R. G. Lambert
Journal: Annals of the Rheumatic Diseases (2020)

Background: The ASAS classification criteria for axial spondyloarthritis (axSpA) have overall sensitivity/specificity of 82.9%/84.4% but component imaging and clinical arms differ in performance (66.2%/97.3% and 56.6%/83.3%, respectively) 1 . Objectives: We aimed to demonstrate that a data-driven elimination of SpA clinical features that were non-discriminatory in comparisons of patients diagnosed with and without axSpA in a prospective cohort of patients with undiagnosed back pain could enhance the performance of the criteria. Methods: We used data from the prospective multicenter Screening for Axial Spondyloarthritis in Psoriasis, Iritis, and Colitis (SASPIC) Study. Consecutive patients ≤45 years of age with ≥3 months undiagnosed back pain with any one of psoriasis, AAU, or colitis undergo routine diagnostic evaluation by a rheumatologist for axial SpA, including imaging assessed by central readers. Univariable and multivariable logistic regression analysis was performed to determine which clinical SpA features were/were not discriminatory for the final diagnosis of axSpA. We then compared the sensitivity and specificity of the ASAS criteria with and without these features. Results: A total of 246 patients were recruited, 47.6% being diagnosed with axSpA (61.5% male, age 33.7 years, symptom duration 7.6 years, B27 positive 52.1%). The following clinical SpA features were non-discriminatory between axSpA/not axSpA: NSAID response, family history of SpA, heel enthesitis, peripheral arthritis, dactylitis. Specificity of the clinical arm and the overall criteria increased from 82.2% to 86.8% without impacting sensitivity. This effect was particularly noteworthy in patients with lower degree of symptomatology (back pain severity &lt;5/10, specificity increases from 76.7% to 90.7%), short symptom duration (&lt;5 years, specificity increases from 78% to 84.7%), and in females (specificity increases from 80.6% to 86.1%). Conclusion: In a prospective cohort with a high pre-test probability of axSpA certain clinical SpA features were not helpful in discriminating a diagnosis of SpA from not-SpA. Deletion of these features from the list of SpA features used in the ASAS classification criteria enhanced the performance of the criteria, especially in female patients and those with early disease. References: [1]Rudwaleit et al. Ann Rheum Dis 2009;68: 777-83 Patient Category Number ASAS criteria Imaging arm Clinical arm Sen Spec Sen Spec Sens Spec All patients 246 65 82.2 36.8 97.7 50.4 82.2 High confidence in diagnosis 190 73.8 84.5 47.5 98.2 56.3 84.5 Patients with back pain ≥5/10 165 63.3 84.9 34.2 98.8 51.9 84.9 Patients with back pain &lt;5 81 68.4 76.7 42.1 95.3 47.4 76.7 Patients with symptom duration ≥5 years 103 71.2 85.7 35.6 97.1 56.2 85.7 Patients with symptom duration &lt;5 years 143 54.5 78 38.6 98.3 40.9 78 Males 129 68.1 84.2 47.2 98.2 48.6 84.2 Females 117 60 80.6 20 97.2 53.3 80.6 After deletion of ‘NSAID response’, ‘Family Hx SpA’, ‘heel enthesitis’, ‘peripheral arthritis’, ‘dactylitis’ SpA features All patients 246 65 86.8 36.8 97.7 50.4 86.8 High confidence in diagnosis 190 73.8 87.3 47.5 98.2 56.3 87.3 Patients with back pain ≥5/10 165 63.3 84.9 34.2 98.8 51.9 84.9 Patients with back pain &lt;5 81 68.4 90.7 42.1 95.3 47.4 90.7 Patients with symptom duration ≥5 years 103 71.2 88.6 35.6 97.1 56.2 88.6 Patients with symptom duration &lt;5 years 143 54.5 84.7 38.6 98.3 40.9 84.7 Males 129 68.1 87.7 47.2 98.2 48.6 87.7 Females 117 60 86.1 20 97.2 53.3 86.1 Disclosure of Interests: Walter P. Maksymowych Grant/research support from: AbbVie, Novartis, Pfizer, and UCB, Consultant of: AbbVie, Boehringer Ingelheim, Celgene, Eli Lilly, Galapagos, Janssen, Novartis, Pfizer, and UCB, Employee of: Chief Medical Officer of CARE Arthritis Limited, Speakers bureau: AbbVie, Janssen, Novartis, Pfizer, and UCB, Raj Carmona: None declared, Jon Chan: None declared, James Yeung: None declared, Sibel Aydin: None declared, Liam Martin: None declared, Ariel Masetto: None declared, Olga Ziouzina: None declared, Stephanie Keeling: None declared, Sherry Rohekar: None declared, Rana Dadashova: None declared, Joel Paschke: None declared, Amanda Carapellucci: None declared, Robert G Lambert: None declared