Comparison of four validated psoriatic arthritis screening tools in diagnosing psoriatic arthritis in patients with psoriasis (COMPAQ Study)

Background Four validated psoriatic arthritis (PsA) screening tools are used for diagnosing PsA in patients with psoriasis. Objectives To evaluate the sensitivity and specificity of the Toronto Psoriatic Arthritis Screen II (ToPAS II), the Psoriatic Arthritis Screening and Evaluation (PASE), the Psoriasis Epidemiology Screening Tool (PEST) and the Early Arthritis for Psoriatic Patients (EARP) questionnaires in diagnosing PsA in patients with psoriasis. Methods This was a noninterventional, cross-sectional study. In total, 302 patients with psoriasis completed all the questionnaires prior to rheumatological evaluation. Patients diagnosed as having a rheumatological disease were excluded. Characteristics of joint involvement in PsA were noted, but details of non-PsA rheumatological diseases were not captured. Results Of 302 patients with psoriasis, 45 (14.9%) had PsA, according to the Classification of Psoriatic Arthritis criteria; 27 (8.9%) had a ToPAS II score >= 8, suggestive of PsA; 36 (11.9%) had a PEST questionnaire score >= 3, suggestive of PsA; 50 (16.5%) had a PASE questionnaire score >= 44 (PASE 44), suggestive of PsA; 47 (15.5%) had a PASE score of 47 (PASE 47; used in development of the PASE questionnaire); and 72 (23.8%) patients had an EARP questionnaire score >= 3, suggestive of PsA. The sensitivities and specificities of EARP, PASE 44, PASE 47, PEST and ToPAS II were 91%, 80%, 76%, 53% and 44%, and 88%, 95%, 95%, 95% and 97%, respectively. Conclusions EARP was found to have the best sensitivity; ToPAS II had the highest specificity. A major limitation of the study design was the exclusion of pre-existing rheumatological diseases.