P56 Validation and comparison of the early arthritis for psoriatic patients questionnaire, the psoriasis epidemiology screening tool and the psoriatic arthritis uncluttered screening evaluation (PURE-4) in a Danish population

Abstract Up to 30% of patients with psoriasis (PsO) develop psoriatic arthritis (PsA). National guidelines recommend screening patients with PsO for PsA; however, there is no consensus on the best-suited method. This study aims to validate and compare three international PsA screening questionnaires (PEST, EARP and PURE-4) in a Danish setting. The English questionnaires were translated and culturally adapted to the Danish language. Adult patients with PsO and without established PsA were recruited from a dermatology department at a university hospital, a private dermatology clinic and the Danish Psoriasis Association. The patients answered the three screening questionnaires in a random order, and all patients were subsequently seen by a rheumatologist who ruled out or verified the diagnosis of PsA according to the CASPAR criteria. The performance of each questionnaire was assessed by determining the sensitivity and specificity at different cut-off values and analysing the receiver operator characteristic (ROC) curves. A total of 114 patients participated in the study. At a cut-off value of ≥3, the PEST questionnaire had a sensitivity of 66.7% and specificity of 67.6%, while the numbers for EARP were 88.9 and 39.0%, respectively. The PURE-4 scale had a sensitivity of 100% and specificity of 26.7% at a cut-off value of ≥ 1. The area under the curve (AUC) for PEST was 0.71 [95% confidence interval (CI): 0.51–0.92]. For EARP, the AUC was 0.75 (95% CI: 0.58–0.91), while PURE-4 had an AUC of 0.67 (95% CI: 0.53–0.82). Optimal cut-off values were determined to be ≥3, ≥6 and ≥2 for PEST, EARP and the PURE-4 scale, respectively. When looking at the questionnaires’ ability to find patients with either rheumatologically verified PsA or probable PsA, meaning likely PsA but not complete fulfilment of the CASPAR criteria, all questionnaires maintained almost the same sensitives and specificities. The questionnaires were successfully cross-culturally validated and had an acceptable performance in line with other translated versions. However, all three questionnaires performed worse than in the original validation studies. The EARP questionnaire had the best discriminatory ability; however, a higher cut-off point for referral should be considered.