Validity and reliability of the Health Assessment Questionnaire among patients with spondyloarthritis in Singapore

AimThe Health Assessment Questionnaire (HAQ) is a popular tool used to measure disability. Few studies have assessed its psychometric properties in patients with spondyloarthritis (SpA). We therefore aimed to assess the reliability and validity of the HAQ in patients with SpA in Singapore. MethodCross-sectional data from a registry of 196 patients with SpA recruited from a dedicated tertiary referral clinic in Singapore from 2011 to 2014 was used. Analyses were guided by the COnsensus-based Standards for the selection of health Measurement INstruments (COSMIN) framework. Internal consistency reliability was assessed using Cronbach's alpha. Convergent construct validity was assessed by 30 a priori hypotheses through correlation of the summary score and the eight domain scores of the HAQ with other health outcome measures: Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), Bath Ankylosing Spondylitis Functional Index (BASFI), Bath Ankylosing Spondylitis Global Score (BASG), pain, Patient's Global Assessment (PGA) and Short Form-36 Health Survey (SF-36). Divergent construct validity was assessed by poor correlation of HAQ with SF-36 Mental component score (MCS). ResultsAmong 196 patients (155 males [79.1%] median [range] age: 36 [17-70]; 166 Chinese [84.7%]), the HAQ showed a high internal consistency of 0.78-0.84. Convergent validity was supported by achieving 26 out of the 30 a priori hypotheses. Divergent validity was also established- correlation of SF-36 MCS with seven domains and summary scores of the HAQ were not statistically significant. ConclusionThis study supports the HAQ as a valid and reliable measure of disability for use in patients with SpA.