Challenges of ASAS criteria in Real-World Colombia SpA patients. A cross-sectional study.

Objective: The Assessment of SpondyloArthritis international Society (ASAS) criteria classify spondyloarthritis (SpA) based on clinical presentation. Although widely applied, their performance in Colombia's population remains unclear. The study aimed to characterize a Colombian SpA cohort, identify factors associated with peripheral SpA (pSpA), compare SpA subtypes, assess the performance of ASAS criteria, and compare them with modified New York (mNY) and European Spondyloarthropathy Study Group (ESSG) criteria.

Methods: This cross-sectional study included patients with newly diagnosed SpA by at least one expert rheumatologist. Participants completed a structured survey, physical examination, imaging, and laboratory tests. Researchers classified patients using ASAS, ESSG, and mNY criteria and compared clinical characteristics across groups. Finally, the performance of the ASAS criteria relative to the rheumatologist's diagnosis, mNY, and ESSG.

Results: The study analyzed 461 SpA patients, of whom 58.1% had pSpA. Patients with axial SpA (axSpA) and pSpA differed significantly in age at onset, initial symptoms, buttock pain, Schober test, sacroiliitis, and HLA alleles. The ASAS criteria demonstrated a sensitivity of 90.8% compared to rheumatologist diagnosis. Notably, 33% of patients classified as ankylosing spondylitis by mNY or ESSG were misclassified as pSpA under ASAS due to unmet entry criteria for axSpA.

Conclusion: This large Colombian SpA cohort, predominantly pSpA, revealed distinct clinical and imaging features between axSpA and pSpA. The ASAS criteria showed high sensitivity but failed to classify a subset of patients with radiographic sacroiliitis as axSpA, highlighting limitations in their entry criteria for axSpA.