Objective: To determine the prevalence of radiographic evidence of sacroiliitis in a large population of patients with psoriatic arthritis.
Patients and design: Patients were recruited from 15 clinical centers. This was part of a large, multicenter study of patients with an established diagnosis of ankylosing spondylitis, psoriatic arthritis, or reactive arthritis. For this cohort, an established diagnosis of psoriatic arthritis was required, with cutaneous manifestations and involvement of at least three appendicular joints. At entry, patients were not selected for the presence of axial involvement. Radiographs - one anteroposterior view of the pelvis and one oblique view of each sacroiliac joint - were graded using the New York classification scale by a musculoskeletal radiologist masked to the specific diagnosis and clinical symptoms. Re-evaluation of 10% of the films 3 years later quantified intraobserver variability.
Results: Two hundred and two patients with psoriatic arthritis were studied. Duration of the disease averaged 12 years; all patients had psoriasis and peripheral arthritis. The prevalence of radiographic evidence of sacroiliitis (grade 2 or higher) was 78%; 71% of these had grade 3 disease.
Conclusions: Previously reported prevalence of sacroiliitis in patients with psoriatic arthritis ranges from 30% to 50%. The prevalence of radiographic evidence of sacroiliitis in this large multicenter cohort of patients with appendicular psoriatic arthritis was substantially higher.