Frequency of undiagnosed psoriatic arthritis among psoriasis patients in Australian dermatology practice.

Background Psoriatic arthritis commonly develops in psoriasis patients and, if undiagnosed, can lead to potentially avoidable joint damage and an increased risk of comorbidity and mortality. Increased awareness of PsA symptoms among dermatologists provides an opportunity for earlier diagnosis, more timely therapy and prevention of disability. Objective To provide Australian epidemiological data on the frequency of undiagnosed PsA among psoriasis patients in dermatology practice, and to investigate the impact of psoriasis on quality of life and work productivity. Methods Nine tertiary centre dermatology practices enrolled patients presenting with plaque psoriasis and no prior rheumatologist-confirmed PsA diagnosis. Patients were screened using the Psoriatic Arthritis Screening and Evaluation (PASE) questionnaire and were referred to a rheumatologist for assessment of PsA status using CASPAR criteria if they had a PASE score ≥44. Results Based on the composite and sequential application of PASE and CASPAR criteria, undiagnosed PsA among psoriasis patients in this study is 9% [95% CI: 6, 12]. The PPV of PASE in this setting is 26% [95% CI: 19, 34]. Nail involvement and chronic large plaque psoriasis were identified as independent positive predictors of PsA, whereas scalp psoriasis was an independent negative predictor of PsA. Patients with moderate-to-severe psoriasis (PASI ≥15) had lower quality of life scores than patients with less severe psoriasis. Conclusion In this study, the frequency of undiagnosed PsA in Australian dermatology practice was 9% among plaque psoriasis patients with no prior PsA diagnosis. Compared with psoriasis alone, the impact of undiagnosed PsA on health-related quality of life of psoriasis patients is substantial.