Background: The Health Assessment Questionnaire Disability Index (HAQDI) is one of the main instruments used to evaluate functional status in rheumatoid arthritis (RA).
Aim: To assess the reliability and validity of the Spanish version of HAQDI in Chilean RA population.
Materials and methods: The questionnaire was applied to 98 patients with RA aged 44 ± 12 years (90% women). Reliability was assessed using Cronbach's alpha statistic for internal consistency. Construct validity was assessed by comparing total HAQDI value and eight HAQDI domains with multiple parameters of disease activity. Discriminant validity was evaluated by classifying disease activity in low, medium or high and evaluating HAQDI value in each category. Floor and ceiling effects were evaluated. To assess construct validity, principal components analysis was performed using varimax rotation.
Results: There were no issues in the comprehensibility of the questionnaire. Mean HAQDI score was 1.57 ± 0.66. Standardized Cronbach's Alpha was 0.883. Correlations between Chilean HAQ domains had a p value less than 0.001, and values ranged from 0.317 to 0.597. Activity parameters, DAS 28 and CDAI were significantly correlated with HAQDI domains. Mean HAQDI values were 0.98 ± 0.59,1.45 ± 0.57, and 1.90 ± 0.56 for mild, moderate and severe disease activity. A principal components analysis identified two factors that accounted for 70.0% of total variability.
Conclusions: This study shows that the Spanish version of HAQDI is reliable and valid and can be used in Chilean patients with RA.