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Extended report
High prevalence of psoriatic arthritis in patients with severe psoriasis with suboptimal performance of screening questionnaires
  1. Muhammad Haroon1,
  2. Brian Kirby2,
  3. Oliver FitzGerald1
  1. 1Department of Rheumatology, St Vincent's University Hospital, Dublin, Ireland
  2. 2Department of Dermatology, St Vincent's University Hospital, Dublin, Ireland
  1. Correspondence to Professor Oliver FitzGerald, Department of Rheumatology, St Vincent's University Hospital, Elm Park, Dublin, 4, Ireland; oliver.fitzgerald{at}


Objectives The objectives of this study were to: (1) assess the prevalence of psoriatic arthritis (PsA) among Psoriasis (Ps) patients attending dermatology clinics; (2) identify clinical predictors of the development of PsA; and (3) compare the performance of three PsA screening questionnaires: Psoriatic Arthritis Screening and Evaluation (PASE), Psoriasis Epidemiology Screening Tool (PEST) and Toronto Psoriatic Arthritis Screening (ToPAS).

Methods Patients were divided into two groups: Group-1, consecutive psoriasis patients attending dermatology clinics with no known diagnosis of inflammatory arthritis and Group-2, consecutive patients attending rheumatology clinics with a confirmed diagnosis of PsA. In Group-1, patients completed the screening questionnaires, followed by a full rheumatological evaluation whether or not they reported musculoskeletal symptoms.

Results 200 patients were recruited with 100 in each group. In all, 84% of patients in dermatology group were using systemic therapy for their skin disease, and 99% of patients in rheumatology group were on systemic immunosuppressives. In Group-1, 29% of patients were diagnosed with PsA after rheumatological evaluation. On univariate and multivariate analyses, there was a significant positive association between Psoriasis Area and Severity Index and a new diagnosis of PsA (p=0.046). Different patterns of joint involvement were noted in patients with newly diagnosed PsA versus patients with established PsA with fewer polyarticular disease presentations (p=0.0001). In Group-1, the PEST, PASE and ToPAS assessments had sensitivities of 27.5%, 24% and 41%, and specificities of 98%, 94% and 90%, respectively. In Group-2, the sensitivities were 86%, 62% and 83%, respectively.

Conclusions 29% of Ps patients attending dermatology clinics had undiagnosed PsA. Psoriasis severity was associated with a new diagnosis of PsA. Poor sensitivities for the screening questionnaires were noted due to inadequate detection of patterns of arthritis other than polyarticular disease.

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