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.