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Psychometric properties of the Quality of Life Inventory-Disability (QI-Disability) measure

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Abstract

Purpose

Children with intellectual disability encounter daily challenges beyond those captured in current quality of life measures. This study evaluated a new parent-report measure for children with intellectual disability, the Quality of Life Inventory-Disability (QI-Disability).

Methods

QI-Disability was administered to 253 primary caregivers of children (aged 5–18 years) with intellectual disability across four diagnostic groups: Rett syndrome, Down syndrome, cerebral palsy or autism spectrum disorder. Exploratory and confirmatory factor analyses were conducted and goodness of fit of the factor structure assessed. Associations between QI-Disability scores, and diagnostic and age groups were examined with linear regression.

Results

Six domains were identified: physical health, positive emotions, negative emotions, social interaction, leisure and the outdoors, and independence. Goodness-of-fit statistics were satisfactory and similar for the whole sample and when the sample was split by ability to walk or talk. On 100 point scales and compared to Rett syndrome, children with Down syndrome had higher leisure and the outdoors (coefficient 10.6, 95% CI 3.4,17.8) and independence (coefficient 29.7, 95% CI 22.9, 36.5) scores, whereas children with autism spectrum disorder had lower social interaction scores (coefficient − 12.8, 95% CI − 19.3, − 6.4). Scores for positive emotions (coefficient − 6.1, 95% CI − 10.7, − 1.6) and leisure and the outdoors (coefficient 5.4, 95% CI − 10.6, − 0.1) were lower for adolescents compared with children.

Conclusions

Initial evaluation suggests that QI-Disability is a reliable and valid measure of quality of life across the spectrum of intellectual disability. It has the potential to allow clearer identification of support needs and measure responsiveness to interventions.

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Abbreviations

ASD:

Autism spectrum disorder

CI:

Confidence interval

DIF:

Differential item functioning

ICF:

International Classification of Functioning, Disability and Health

PedsQL:

Pediatric Quality of Life Inventory

QI-Disability:

Quality of Life Inventory-Disability

QOL:

Quality of life

SD:

Standard deviation

WA:

Western Australia

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Acknowledgements

We thank the families for their participation in this study. We acknowledge the database infrastructures necessary for the current study. The authors thank the Disability Services Commission WA in establishing the Down syndrome database, and community organisations Developmental Disability WA and the Down Syndrome Association of Western Australia for their support. We thank the Australian Paediatric Surveillance Unit (APSU) and the Rett Syndrome Association of Australia for their ongoing support in case ascertainment for the Australian Rett Syndrome Database. The Australian Rett Syndrome Study was previously supported by the National Institute of Health Grant 5R01HD043100-05 and National Health and Medical Research Council project Grants #303189 and #1004384. The Victorian Cerebral Palsy Register receives funding from the Victorian Department of Health and Human Services and from the Victorian Government’s Operational Infrastructure Support Program for support for register staff. We acknowledge the support of Dr Sue Reid in the recruitment of families with a child with cerebral palsy and Dr Emma Glasson who supported the recruitment of families from the WA Autism Registry. This study is currently funded by the National Health and Medical Research Council (#1103745). ED was previously supported by a Victorian Health Promotion Public Health Fellowship. AW and HL are each supported by a Senior Research Fellowship from the National Health and Medical Research Council (#1077966 and #1117105, respectively). KW in funded by the Apex Foundation for Research into Intellectual Disability and the Royal Children’s Hospital Foundation. DR is funded by a University of Melbourne Award. The funders of this research have had no roles in the study design, data collection, data analysis, manuscript preparation and/or publication decisions.

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Authors and Affiliations

  1. Telethon Kids Institute, The University of Western Australia, P.O. Box 855, Perth, WA, 6872, Australia

    Jenny Downs, Peter Jacoby, Helen Leonard, Amy Epstein, Nada Murphy & Andrew Whitehouse

  2. School of Physiotherapy and Exercise Science, Curtin University, Perth, WA, Australia

    Jenny Downs

  3. The Jack Brockhoff Child Health and Wellbeing Program, Melbourne School of Population and Global Health, The University of Melbourne, Melbourne, VIC, Australia

    Elise Davis

  4. Department of Neurodevelopment and Disability, Royal Children’s Hospital, Melbourne, VIC, Australia

    Dinah Reddihough & Katrina Williams

  5. Department of Paediatrics, The University of Melbourne, Melbourne, VIC, Australia

    Dinah Reddihough & Katrina Williams

  6. Murdoch Children’s Research Institute, Melbourne, VIC, Australia

    Dinah Reddihough & Katrina Williams

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  1. Jenny Downs
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  2. Peter Jacoby
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  3. Helen Leonard
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Correspondence to Jenny Downs.

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Downs, J., Jacoby, P., Leonard, H. et al. Psychometric properties of the Quality of Life Inventory-Disability (QI-Disability) measure. Qual Life Res 28, 783–794 (2019). https://doi.org/10.1007/s11136-018-2057-3

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