title: Measuring disability experienced by adults living with HIV: assessing construct validity of the HIV Disability Questionnaire using confirmatory factor analysis.
abstract: OBJECTIVE
  To assess the construct validity of the HIV Disability Questionnaire (HDQ), a self-administered questionnaire that describes the presence, severity and episodic nature of disability experienced by people living with HIV.
  
  
  METHODS
  We conducted a confirmatory factor analysis. We hypothesised that domains in the HDQ characterised six dimensions of disability, each represented by HDQ items: physical symptoms and impairments (20 items); cognitive symptoms and impairments (3 items); mental and emotional health symptoms and impairments (11 items); uncertainty (14 items); difficulties with day-to-day activities (9 items) and challenges to social inclusion (12 items). We developed a measurement model to test these hypotheses. We used maximum likelihood methods of estimation to determine model fit. We considered a threshold for the Root Mean Square Error of Approximation (RMSEA) of <0.05 as an indication of overall goodness of model fit. We considered variables with factor loadings of >0.30 as representing a given domain of disability.
  
  
  METHODS
  We recruited adults with HIV from hospital clinics, AIDS service organisations and a specialty hospital in Ontario.
  
  
  METHODS
  Of the 361 adults with HIV who completed the HDQ, 80% were men, 36% were 50 or older and 77% reported living with at least two concurrent health conditions in addition to HIV.
  
  
  METHODS
  We administered the HDQ followed by a demographic questionnaire.
  
  
  RESULTS
  The model achieved good overall fit as indicated by a RMSEA of 0.030 (90% CI 0.028 to 0.033). All HDQ items represented our hypothesised dimensions of disability (factor loadings >0.30). Factor loadings ranged from 0.34 to 0.90. Domains of disability correlated with each other ranging from r=0.47 (between difficulties with day-to-day activities and uncertainty) to r=0.88 (between mental-emotional health challenges and challenges to social inclusion).
  
  
  CONCLUSIONS
  The six domain structure of the HDQ demonstrated construct validity when administered to adults living with HIV.
authors.affiliation: Department of Physical Therapy, University of Toronto, Toronto, Ontario, Canada School of Rehabilitation Science, McMaster University, Hamilton, Ontario, Canada Institute of Health Policy, Management and Evaluation, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Kelly K
authors.initials: KK
authors.lastname: O'Brien
authors.affiliation: School of Rehabilitation Science, McMaster University, Hamilton, Ontario, Canada.
authors.forename: Patricia
authors.initials: P
authors.lastname: Solomon
authors.affiliation: Institute of Health Policy, Management and Evaluation, University of Toronto, Toronto, Ontario, Canada Centre for Research on Inner City Health, Keenan Research Centre of the Li Ka Shing Knowledge Institute, St Michael's Hospital, Toronto, Ontario, Canada Department of Medicine, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Ahmed M
authors.initials: AM
authors.lastname: Bayoumi
mesh_terms: D000203:Activities of Daily Living; D000328:Adult; D003071:Cognition; D004185:Disability Evaluation; D005163:Factor Analysis, Statistical; D005260:Female; D015658:HIV Infections / Q000503:physiopathology / Q000523:psychology*; D006304:Health Status; D006801:Humans; D008297:Male; D008875:Middle Aged; D012929:Psychological Distance; D015203:Reproducibility of Results; D011795:Surveys and Questionnaires; D035501:Uncertainty
keywords: Disability; REHABILITATION MEDICINE