Reliability and validity of a new HIV-specific questionnaire with adults living with HIV in Canada and Ireland: the HIV Disability Questionnaire (HDQ)

BACKGROUND: Our aim was to assess internal consistency reliability, construct validity, and test-retest reliability of the HDQ with adults living with HIV in Canada and Ireland. METHODS: We recruited adults 18 years of age or older living with HIV from hospital clinics and AIDS service organizations in Canada and Ireland. We administered the HDQ paired with reference measures (World Health Organization Disability Assessment Schedule, SF-36 Questionnaire, Medical Outcomes Study Social Support Survey), and a demographic questionnaire. We calculated HDQ disability presence, severity and episodic scores (scored from 0–100). We calculated Cronbach’s alpha and Intraclass Correlation Coefficients (ICC) (Canada only) for the disability severity and episodic scores and considered coefficients >0.80 and >0.70 as acceptable, respectively. To assess construct validity, we tested 40 a priori hypotheses of correlations between scores on the HDQ and reference measures and two known group hypotheses comparing HDQ presence and severity scores based on age and comorbidity. We considered acceptance of at least 75 % of hypotheses as demonstrating support for construct validity. RESULTS: Of the 235 participants (139 Canada; 96 Ireland), the majority were men (74 % Ireland; 82 % Canada) and were taking antiretroviral therapy (88 % Ireland; 91 % Canada). Compared with Irish participants, Canadian participants were older (median age: 48 versus 41 years) and reported living with a higher median number of comorbidities (4 versus 1). Cronbach’s alpha for Irish and Canadian participants were 0.97 (95 % confidence interval (CI): 0.97–0.98) and 0.96 (95 % CI: 0.95–0.98), respectively, for the severity scale and 0.98 (95 % CI: 0.97–0.98) and 0.96 (95 % CI: 0.95–0.98), respectively, for the episodic scale. Of the 40 construct validity correlation hypotheses, 32 (80 %) and 22 (55 %) were supported among the Canadian and Irish samples respectively; both (100 %) known group hypotheses were also supported. ICC values for Canadian participants ranged from 0.80 (95 % CI: 0.71, 0.86) in the cognitive domain to 0.89 (95 % CI: 0.83, 0.92) in the social inclusion domain. CONCLUSIONS: The HDQ demonstrates internal consistency reliability and a variable degree of construct validity when administered to adults living with HIV in Canada and Ireland. The HDQ demonstrates test-retest reliability when administered to adults with HIV in Canada. Further validation of the HDQ outside of Canada is needed. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12955-015-0310-9) contains supplementary material, which is available to authorized users.