Background Delay in diagnosis of psoriatic arthritis (PsA) remains a significant contributor to poor patient outcome. Clinical predictors of the development of arthritis among patients with psoriasis (Ps) have been proposed and a number of screening questionnaires have been developed.
Objectives The objectives of this study were: 1) to assess the prevalence of PsA among Ps patients attending dermatology clinics; 2) to identify clinical predictors of the development of PsA; and 3) to compare the performance of 3 PsA screening questionnaires [Psoriatic Arthritis Screening and Evaluation (PASE), Psoriasis Epidemiology Screening Tool (PEST), and the Toronto Psoriatic Arthritis Screening tool (ToPAS)].
Methods This study was carried out in general dermatology and rheumatology clinics. Patients were divided into two groups: group 1, consecutive patients with skin psoriasis attending dermatology clinics who have no known diagnosis of inflammatory arthritis; group 2, consecutive patients attending rheumatology clinics with a confirmed diagnosis of PsA. The diagnosis of PsA was made using the CASPAR criteria. In group 1, patients completed the screening questionnaires, which were followed by a thorough rheumatologic evaluation whether or not patients reported musculoskeletal symptoms.
Results 200 patients were recruited; 100 in each group. 84% of patients in Group1 were using systemic therapy for their skin disease, and 99% of patients in Group 2 were on systemic immunosuppressives. In Group 1, 29% of patients were diagnosed with PsA after rheumatologic evaluation. Compared to Group 2, patients in Group1 had significantly higher PASIs (p=0.001), more scalp psoriasis at the time of assessment (p=0.0001) and less nail disease ever in the disease course (p=0.04). There was no significant difference in the presence of scalp disease ever in the disease course among Group 1, Group 2 and even in the subgroup of newly diagnosed patients with PsA.
On univariate and multivariate analysis, the only significant positive association was noted between high PASIs and the new diagnosis of PsA (p=0.046), even after adjusting for confounders such as, age, gender, use of TNFi, duration of psoriasis and the presence of nail and scalp disease ever in the disease course. A strikingly different pattern of joint involvement was noted in patients with newly diagnosed PsA vs. patients with established PsA with fewer non-polyarticular disease (p=0.0001).
In Group 1, the PEST, PASE and ToPAS had sensitivities of 27.5%, 24% and 41%, and specificities of 98%, 94% and 90%, respectively; however, in Group 2, the sensitivities were 86%, 62% and 83%, and specificities were 98%, 94% and 90%, respectively.
Conclusions When patients with known PsA were excluded, 29% of Ps patients attending dermatology clinics had PsA diagnosed following rheumatologic assessment. Psoriasis severity as measured by PASI was associated with the diagnosis of PsA even after adjusting for the use of TNFi, duration of psoriasis, and the presence of nail or scalp disease. Nail disease ever in the disease course was commoner in patients with known PsA. Poor sensitivities for the screening questionnaires was noted among patients with psoriasis, perhaps due in part to inadequate recognition of patterns of arthritis other than that of polyarticular disease.
Disclosure of Interest None Declared