Performance of the 2025 ASAS-Spartan Revised Classification Criteria for Axial Spondyloarthritis in a Canadian Multicenter Inception Cohort with Psoriasis, Uveitis, or Colitis Presenting with Undiagnosed Back Pain

Objectives To test the performance of the 2025 ASAS-SPARTAN Revised Classification Criteria for Axial Spondyloarthritis (axSpA)[1] in a multicenter inception cohort of patients with undiagnosed chronic back pain attending dermatology, ophthalmology, and gastroenterology clinics with psoriasis (PsO), acute anterior uveitis (AAU), or inflammatory bowel disease (IBD) referred to a rheumatologist with special expertise in axSpA. Methods The multicenter Screening for Axial Spondyloarthritis in Psoriasis, Iritis, and Colitis (SASPIC) Study at 9 sites is aimed at early detection of axSpA in consecutive patients presenting with undiagnosed back pain to the rheumatologist. Consecutive patients ≤45 years of age with ≥3 months undiagnosed back pain with any 1 of psoriasis, acute anterior uveitis (AAU), or colitis diagnosed by the relevant specialist had routine clinical evaluation by a rheumatologist for axial SpA. The rheumatologist determined the presence or absence of axial SpA at 3 consecutive stages: 1. After clinical evaluation; 2. After results of labs (B27, CRP), radiography; 3. After results of MRI evaluation. All MRI scans were evaluated by 3 central readers whether the MRI was indicative of axSpA. In SASPIC 1 patients had MRI done as deemed appropriate by the rheumatologist, whereas all patients in SASPIC-2 had MRI. Final diagnosis by the rheumatologist was used as gold standard to test the performance of the criteria according to sensitivity and specificity [95% CI], emphasis being on attainment of high specificity. Results A total of 363 patients were recruited to the SASPIC cohorts (n=212 SASPIC 1, n=151 SASPIC 2) of whom 308 had MRI evaluation. The proportions of patients diagnosed with axSpA were 46.7%, 61.6%, and 46.8% for those with PsO, AAU, and IBD, respectively, in SASPIC-1, whereas the respective proportions were 23.5%, 57.9%, and 23.3% for SASPIC-2. Patient demographics and disease characteristics were similar between those with and without an MRI scan and with the patients recruited to the 2025 ASAS-SPARTAN cohort from which the criteria were developed. Sensitivity/specificity [95% CI] were 56.5 [47.3-65.3]/98.9 [96.1-99.9] for the entire cohort, and 59.7 [46.4-71.9]/ 97.6 [87.1-99.9], 52.8 [35.5-69.6]/ 100.0 [95.8-100.0], 53.9 [33.4-73.4]/ 98.3 [90.8-100.0] for the subgroups with AAU, IBD, or PsO, respectively. Performance in the 2025 ASAS-SPARTAN cohort using central reader imaging data was 56.6 [49.2, 63.7]/ 98.5 [96.5, 99.4] in testing data and 63.1 [56.1, 69.5]/98.7 [96.8, 99.5] in validation data. Conclusion The revised axSpA criteria perform with consistently high specificity in the 2025 ASAS-SPARTAN and SASPIC cohorts. References [1.] Maksymowych W. [Abstract]. Arthritis Rheumatol 2025;77 Suppl 9. https://acrabstracts.org/abstract/the-assessments-in-spondyloarthritis-international-society-asas-and-spondyloarthritis-research-and-treatment-network-spartan-revised-classification-criteria-for-axial-spondyloarthritis-developmen/