1431: Radiographic Sacroiliitis in Psoriatic Arthritis: Clinical, Laboratory, and Spinal Radiographic Correlates in an Indian Cohort

Background/Purpose: Axial involvement in psoriatic arthritis (PsA) is variable and influences treatment choices. Data on axial PsA in Indian patients, especially its clinical and radiographic features, are limited. We aimed to describe these features and their association with radiographic sacroiliitis in an Indian PsA cohort.

Methods: Patients with PsA fulfilling CASPAR criteria were enrolled between April 2024 and March 2025. Demographic, clinical, and laboratory data were collected. Pelvis and spine radiographs were independently scored for sacroiliitis (modified New York criteria) and spinal damage by modified Stokes ankylosing spondylitis score (mSASSS). Patients were stratified by sacroiliitis status, and group comparisons were made using appropriate statistical tests and odds ratios (ORs).

Results: Of 182 consecutively enrolled patients (table 1), radiographic sacroiliitis was present in 85 (46.7%). Thirty of these 85 (35%) radiographic sacroiliitis patients had no clinical axial symptoms. Asymmetric oligoarthritis was the most common pattern of presentation observed as per Moll and Wright Classification (figure-1A). Radiographic sacroiliitis patients were older (mean age 49.6 vs. 45.3 years, p=0.01), had longer disease duration (median 6 vs. 3 years, p=0.01). Axial symptoms (spondylitis ± inflammatory back pain) were more frequent in the sacroiliitis group (51.9% vs. 29.9%, p=0.04; OR 2.5, 95% CI 1.3–4.6), including HLA-B*27 positivity (16.9% vs. 1.0%, p< 0.001; OR 19.2, 95% CI 2.4–151.0). Other clinical features, including peripheral disease patterns, nail changes, enthesitis, dactylitis, and inflammatory markers did not significantly differ.

On spinal radiography (table 2), lumbosacral (LS) spine bridging syndesmophytes were significantly more frequent (35.3% vs. 8.0%, p< 0.001; OR 6.3, 95% CI 2.5–15.0), and LS spine mSASS were higher (median 8 vs. 4, p=0.001). Cervical spine syndesmophytes were also more common in the sacroiliitis group (70.6% vs. 54.4%, p=0.03). The C5, C6, and L4 vertebrae were most frequently involved, and were also frequently damaged with syndesmophytes including non-marginal bridging ones (figure-1B). Though age at onset, age >40 years, history of inflammatory back pain, MASES, Bath Ankylosing Spondylitis Metrology Index (BASMI) components, restriction of cervical rotation, cervical spine radiological changes including bridging syndesmophytes as well as mSASSS were also significantly higher on univariate analysis. But on multivariate logistic regression only HLA-B*27, LS spine bridging syndesmophytes emerged as independent predictors of radiographic sacroiliitis (figure-1C), while shorter disease duration was associated with low odds of radiographic sacroiliitis.

Conclusion: Radiographic sacroiliitis was prevalent in nearly 47% patients in this Indian PsA cohort, often occurring without clinical axial symptoms. HLA-B*27 positivity, and LS spine bridging syndesmophytes were significantly associated with sacroiliitis, while those with disease duration < 2 years had a lower odds of sacroiliitis. These findings support the role of early routine imaging to detect subclinical axial involvement and guide management.