Ab0960 Proposed Modification of the Asas Criteria for a More Natural Classification of Spa

Background: The Assessment of Spondyloarthritis International Society (ASAS) classification criteria are essential for epidemiological data and clinical trials (1). However, in specific clinical scenarios, these criteria may not be adequate because spondyloarthritis (SpA) has a fluctuating course, and only sometimes is the predominant clinical presentation clearly defined, leading to misclassification of SpA patients. Objectives: The present study proposes modifying axial SpA (axSpA) criteria to address this problem. Methods: The cohort was obtained from three referral institutions in Colombia from 1990 to 2015. Patients were diagnosed according to rheumatologist criteria and later were classified according to ASAS criteria. Patients who have less than three months of back pain and radiographic sacroiliitis at the time of the evaluation were allowed to be classified as axSpA if they met the other characteristics proposed by ASAS; this group of patients was called "axSpA - without chronic back pain" (axSpA-w/oCBP). Results: The cohort comprised 461 SpA patients (GESPA cohort). According to the ASAS criteria, the peripheral SpA (pSpA) presentation was the most frequent (58.1%), followed by axial SpA (axSpA) in 32.8%. However, 9.1% of patients did not meet ASAS criteria. The graph presents in bold the patients misclassified according to the different SpA classifications, with about 33% of the pSpA with ankylosis. Modifying the entry criteria for axSpA was made (axSpA-w/oCBP), which allowed 32.8% (88 patients) to be reclassified from pSpA to axSpA. This modification permitted axSpA to be the most frequent clinical presentation (51.8%) without modifying the number of unclassified patients (9.1%). Patients with axSpA-w/oCBP had an earlier onset of the disease, a longer delay in diagnosis, more back pain, and sacroiliitis compared to pSpA (Table 1). Sacroiliitis in MRI/X-ray and HLA-B27 alleles were more frequent in axSpA-w/oCBP, while the HLA-B15 allele was more frequent in pSpA. The inflammation measure by ERS was higher in axSpA-w/oCBP than pSpA. Conclusion: This modification improved the classification of SpA subgroups with fewer pSpA with axial involvement and inflammation, leading to better differentiation between axial and peripheral clinical presentations. This change could positively impact early treatment and significant outcomes. REFERENCES: Rudwaleit M, van der Heijde D, Landewé R, et al. The development of Assessment of SpondyloArthritis international Society classification criteria for axial spondyloarthritis (part II): validation and final selection. Ann Rheum Dis. 2009 Jun;68(6):777-83. Acknowledgements: NIL. Disclosure of Interests: None declared.