Construct validity, reliability, and threshold value for treatment goals of the Thai version of the 12‐item Psoriatic Arthritis Impact of Disease Questionnaire for patients with psoriatic arthritis.

Objective: To determine the construct validity, reliability, and treatment goal threshold of a Thai‐language version of the 12‐item Psoriatic Arthritis Impact of Disease (Thai‐PsAID) questionnaire in patients with psoriatic arthritis (PsA). Methods: This cross‐sectional study involved administering the proposed Thai‐PsAID to 117 Thai patients with PsA. Reliability was assessed by Cronbach's α test and intraclass correlation coefficient (ICC). Construct validity was assessed using Spearman correlation with clinical disease activity index for psoriatic arthritis (cDAPSA), the Health Assessment Questionnaire (HAQ), EQ‐5D index, and the patient‐acceptable symptom state (PASS). The optimal cutoff score of the Thai‐PsAID for minimal disease activity (MDA) was determined by receiver operating characteristic curves. Results: Participants had a mean age of 49.5 years, 61 (52.1%) were female, and the median disease duration was 5 years. The median Thai‐PsAID score was 2.1, with a Cronbach's α coefficient of.95 and an ICC of 0.77. The mean time to complete the Thai‐PsAID was 2.1 min, with no missing data. The Thai‐PsAID score demonstrated a moderate correlation with the cDAPSA, HAQ, and EQ‐5D with indices (Spearman's rho of.64,.54, and −.55, respectively). The cutoff of 2.7 has 81%–84% sensitivity and 69%–85% specificity for classifying patients with MDA, satisfied PASS, and indicating no need to escalate medication. Conclusions: The Thai‐PsAID is a valid, reliable, and feasible tool for measuring PsA prognosis. A cutoff of 2.7 accurately discriminates MDA and PASS and indicates no need for medication escalation. The Thai‐PsAID may be used as a standalone measure. [ABSTRACT FROM AUTHOR]