Supplementary Material for: Arthritis Hit Rate in Patients with Psoriasis Referred for Rheumatology Evaluation

proportion of patients with psoriasis causing pain and impaired quality of life. Early recognition and treatment are important as PsA may result in structural joint damage with a risk of reduced physical function. Objectives: The aim of this study was to determine the proportion of psoriasis patients with suspicion of PsA who are diagnosed with PsA or other rheumatologic conditions following referral from a dermatology department. Furthermore, the study aimed to identify clinical and patient-reported variables identifying patients with psoriasis in whom joint discomfort is an expression of PsA. Methods: This single-center retrospective study included all patients with psoriasis who had been referred for rheumatological evaluation on suspicion of PsA in the period from 2014 to 2018. Results: A total of 364 patient records were reviewed. This identified 106 patients with psoriasis who had been referred for rheumatologic evaluation on suspicion of PsA. Patients with a previous diagnosis of PsA were excluded from the analysis. Among the referred patients, 23.6% were diagnosed with either peripheral or axial PsA, or both. A total of 23.6% were diagnosed with osteoarthritis and an additional 14.2% were diagnosed with inactive PsA. For patient-reported swollen joints and dermatologist-assessed swollen joints at referral, the positive predictive values/negative predictive values for a PsA diagnosis were 40%/100% and 50%/92%, respectively. Conclusion: In this study, 23.6% of patients with psoriasis with symptoms suggestive of PsA were diagnosed with axial and/or peripheral arthritis following rheumatologic evaluation. Patient-reported swollen joints and dermatologist-assessed swollen joints indicated a high likelihood of peripheral PsA. Additionally, the absence of patient-reported swollen joints indicated a very low probability of establishing a diagnosis of peripheral PsA.