Validation of the Thai version of the health assessment questionnaire for patients with psoriatic arthritis

Objective: To validate the Thai version of the Health Assessment Questionnaire (HAQ) for patients with psoriatic arthritis (PsA). Methods: The Thai version of the HAQ was administered to 47 patients with PsA attending our rheumatology clinic. Clinical assessments included the measures of disease activity, disease severity and functional status. The correlation of the single items and total score of the Thai HAQ with the measures of disease activity, disease severity and functional status was assessed using Pearson's correlation or Spearman rank correlation, as appropriate. Results: Of 47 patients who fulfilled the Classification Criteria for Psoriatic Arthritis (CASPAR), 21 were male. Their mean age ± standard deviation (SD) and mean disease duration ± SD were 49 ± 10 years and 6.97 ± 6.17 years, respectively. Spondylitis was the most common manifestation (38%). The mean Thai HAQ score was 0.47. The single items and total score of the Thai HAQ were moderately to highly correlated with several measures of disease activity (r = 0.32-0.81, P < 0.01), except for swollen joint count (r = 0.16). For functional status and disease severity, the Thai HAQ was moderately correlated with grip strength (r = -0.39, P < 0.01), but poorly correlated with the range of spinal movement and the number of damaged joints. (r = -0.01 to 0.17). Cronbach's alpha coefficient for internal consistency reliability was 0.88. These results were comparable to the original version. Conclusion: The Thai version of the HAQ is valid for assessing functional status in patients with PsA; however, its validity may be limited in patients who have axial involvement or permanent joint damage.