Measuring disability experienced by adults living with HIV: assessing construct validity of the HIV Disability
Kelly K O'Brien1, Patricia Solomon2, Ahmed M Bayoumi3
1Department 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.
Objectives:
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.
Design:
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.
Setting:
We recruited adults with HIV from hospital clinics, AIDS service organisations and a specialty hospital in Ontario.
Participants:
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.
Outcome Measures:
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.
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