To compare clinical aspects, disease activity, spinal mobility, and radiographic findings between ankylosing spondylitis (AS) and axial psoriatic arthritis (axPsA) patients

Fifty-eight AS and 42 axPsA patients were enrolled. Patients were assessed by clinical examination, spinal mobility measurements, and conventional radiographs of the sacroiliac joints, lumbosacral and cervical spines. Bath.

AS Metrology Index (BASMI) and modified Stoke AS Spinal Score (mSASSS) were measured. Spondyloarthritis Research Consortium of Canada (SPARCC) enthesitis index score and AS Disease Activity Score (ASDAS) were assessed. Results: The mean age of AS and AxPsA patients were comparable (37.2 ± 11.2 years vs 39.6 ± 13.3 years;p = 0.33) and male:female was 2.63 vs 0.24:1 (p < 0.0001). Inflammatory back pain (IBP) was higher in AS (93.1%) than axPsA (76.2%). Peripheral arthritis was higher in axPsA (85.7%) than in AS (39.7%). Dactylitis and nail dystrophy were present only in axPsA (33.3% and 28.6% respectively) while uveitis was more common in AS (60.3%vs 28.6%;p = 0.12). SPARCC score was higher in axPsA (p = 0.12).The median BASMI was higher in AS (2.1) than axPsA (1.2)(p = 0.07). The mSASSS was similar (AS:19.6 ± 4.7;6–40 and axPsA:14.4 ± 2.1;0–32)(p = 0.23). 63.8% of AS patients had grade 3 sacroiliitis while 61.9% of axPsA had grade 2. 75.9% of AS had high ASDAS while 33.3% of axPsA patients had very high activity (p = 0.039).

AS patients were more likely to be males, smoked, higher IBP, lower peripheral arthritis, more uveitis, higher limitation in spinal mobility measurements, more spinal deformities, and severe radiographic involvement with nearly equal disease activity as in axPsA patients.