Framing of mobility items: a source of poor agreement between preference-based health-related quality of life instruments in a population of individuals receiving assisted ventilation
To explore the influence of descriptive differences in items evaluating mobility on index scores generated from two generic preference-based health-related quality of life (HRQoL) instruments.
The study examined cross-sectional data from a postal survey of individuals receiving assisted ventilation in two state/province-wide home mechanical ventilation services, one in British Columbia, Canada and the other in Victoria, Australia. The Assessment of Quality of Life 8-dimension (AQoL-8D) and the EQ-5D-5L were included in the data collection. Graphical illustrations, descriptive statistics, and measures of agreement [intraclass correlation coefficients (ICCs) and Bland–Altman plots] were examined using index scores derived from both instruments. Analyses were performed on the full sample as well as subgroups defined according to respondents’ self-reported ability to walk.
Of 868 individuals receiving assisted ventilation, 481 (55.4%) completed the questionnaire. Mean index scores were 0.581 (AQoL-8D) and 0.566 (EQ-5D-5L) with ‘moderate’ agreement demonstrated between the two instruments (ICC = 0.642). One hundred fifty-nine (33.1%) reported level 5 (‘I am unable to walk about’) on the EQ-5D-5L Mobility item. The walking status of respondents had a marked influence on the comparability of index scores, with a larger mean difference (0.206) and ‘slight’ agreement (ICC = 0.386) observed when the non-ambulant subgroup was evaluated separately.
This study provides further evidence that between-measure discrepancies between preference-based HRQoL instruments are related in part to the framing of mobility-related items. Longitudinal studies are necessary to determine the responsiveness of preference-based HRQoL instruments in cohorts that include non-ambulant individuals.
KeywordsAQoL-8D EQ-5D-5L Mobility Quality of life Respiratory insufficiency Non-invasive ventilation
Compliance with ethical standards
LMH received financial support in the form of a Postgraduate Scholarship from the National Health and Medical Research Foundation (Australia).
Conflict of interest
DGTW and SB are members of the EuroQol Group. CFM has been an advisory board member for Pfizer, Boehringer Ingelheim, Astra Zeneca, and Novartis, and has received lecture fees from GlaxoSmithKline. MEH has received an unrestricted research Grant and travel support from ResMed and an equipment loan from Philips Respironics. LMH, DJB, and JDR declare no conflicts of interest.
All procedures performed involving human participants were in accordance with the ethical standards of the institutional research committees [University of British Columbia Clinical Research Ethics Board (approval H12-01479) and the Austin Health Research Ethics Committee (approval H2012/04850)] and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
Informed consent was obtained from all individual participants included in the study.
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