title: Validity and reliability of the Health Assessment Questionnaire among patients with spondyloarthritis in Singapore.
abstract: OBJECTIVE
  The 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.
  
  
  METHODS
  Cross-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).
  
  
  RESULTS
  Among 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.
  
  
  CONCLUSIONS
  This study supports the HAQ as a valid and reliable measure of disability for use in patients with SpA.
authors.affiliation: Program in Health Systems and Services Research, Duke-NUS Medical School, Singapore, Singapore.
authors.forename: Yu Heng
authors.initials: YH
authors.lastname: Kwan
authors.affiliation: Department of Rheumatology and Immunology, Singapore General Hospital, Singapore, Singapore.
authors.forename: Warren
authors.initials: W
authors.lastname: Fong
authors.affiliation: Department of Rheumatology and Immunology, Singapore General Hospital, Singapore, Singapore.
authors.forename: Nai Lee
authors.initials: NL
authors.lastname: Lui
authors.affiliation: Department of Rheumatology and Immunology, Singapore General Hospital, Singapore, Singapore.
authors.forename: Si Ting
authors.initials: ST
authors.lastname: Yong
authors.affiliation: Centre of Quantitative Medicine, Duke-NUS Medical School, Singapore, Singapore.
authors.forename: Yin Bun
authors.initials: YB
authors.lastname: Cheung
authors.affiliation: Program in Health Systems and Services Research, Duke-NUS Medical School, Singapore, Singapore.|Centre of Ageing Research and Education, Duke-NUS Medical School, Singapore, Singapore.
authors.forename: Rahul
authors.initials: R
authors.lastname: Malhotra
authors.affiliation: Program in Health Systems and Services Research, Duke-NUS Medical School, Singapore, Singapore.|Department of Rheumatology and Immunology, Singapore General Hospital, Singapore, Singapore.
authors.forename: Julian
authors.initials: J
authors.lastname: Thumboo
authors.affiliation: Program in Health Systems and Services Research, Duke-NUS Medical School, Singapore, Singapore.
authors.forename: Truls
authors.initials: T
authors.lastname: Østbye
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D003430:Cross-Sectional Studies; D004185:Disability Evaluation; D005260:Female; D006304:Health Status; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012042:Registries; D015203:Reproducibility of Results; D012846:Singapore; D025241:Spondylarthritis / Q000175:diagnosis*; D011795:Surveys and Questionnaires; D055815:Young Adult
keywords: 
  HAQ
  ; Singapore; psychometrics; spondyloarthritis; validity