Inflammatory joint manifestations are prevalent in psoriasis: prevalence study of joint and axial involvement in psoriatic patients, and evaluation of a psoriatic and arthritic questionnaire.

To examine the prevalence of inflammatory manifestations, such as peripheral arthritis, axial disease, undifferentiated spondyloarthropathy (uSpA) and enthesopathies in patients with psoriasis, and to evaluate a psoriatic and arthritic questionnaire (PAQ) to identify patients with arthritis. Methods. An evaluation of a questionnaire (PAQ) in a hospital- and community-based population of 276 psoriatic patients, and clinical, radiological, and laboratory examination of the 202 patients answering the questionnaire and willing to participate in the subsequent study. Results. Ninety-seven patients (48%) were identified as having, or having had, inflammatory manifestations (peripheral arthritis, axial disease, uSpA, and enthesopathies). Sixty-seven patients (33%) had peripheral arthritis and/or axial disease, 30 of whom had not previously been diagnosed. A total PAQ score of 4 out of 8 was the best cutoff value detecting arthritis with a sensitivity of 60% and a specificity of 62.2%. A positive answer to the question "Have you ever thought you might have arthritis?" in combination with morning stiffness in peripheral joints for at least 60 min, had a sensitivity of 30% and a specificity of 91.1% and was significantly associated with peripheral arthritis and/or axial disease in multiple logistic regression analysis. Conclusion. We found a high prevalence of inflammatory joint/axial disease in this group of psoriatic patients. Almost half the patients with peripheral arthritis and/or axial disease had not previously been diagnosed. The PAQ did not, either as a total score or by combining questions, discriminate for arthritis in this population with psoriasis.