Best practice for developing and validating a quality of life measure for children with intellectual disability

A/Professor Jenny Downs1, A/Prof Peter Jacoby1, A/Prof Helen Leonard1, Ms Amy Epstein1, Ms Nada Murphy1, Professor Dinah Reddihough2, Professor Andrew Whitehouse1, Professor Katrina Williams3

1Telethon Kids Institute, Perth, Australia, 2Murdoch Children’s Research Institute, Melbourne, Australia, 3Department of Paediatrics, Monash University, Melbourne, Australia

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

We conducted 77 interviews parents of a 5-18-year-old child with intellectual disability (Down syndrome, Rett syndrome, cerebral palsy or autism spectrum disorder) and identified 50 questionnaire items from the data. These items were administered to 16 parents using cognitive interviewing (“think aloud”) and 41 items were retained for piloting with 253 primary caregivers. Exploratory and confirmatory factor analyses were conducted. Associations between diagnostic and age groups and QI-Disability scores were examined with linear regression.

Six factors were identified from 32 of the 41 items: physical health, positive emotions, negative emotions, social interaction, leisure and the outdoors, and independence. Compared to Rett syndrome, children with Down syndrome had higher leisure and the outdoors and independence scores, whereas children with autism spectrum disorder had lower social interaction scores. Scores for positive emotions and leisure and the outdoors were lower for adolescents compared with children.

Ongoing consumer feedback shaped the development of QI-Disability. Initial evaluation suggests that QI-Disability is a reliable and valid measure of quality of life across the spectrum of intellectual disability. Use of QI-Disability for children with intellectual disability will allow clearer identification of support needs and measure responsiveness to interventions.


Dr Jenny Downs leads research programs at the Telethon Kids Institute in Perth, Western Australia that work towards improving outcomes for children with disability and their families. Her current program includes research on rare disorders including Rett syndrome, the CDKL5 Deficiency Disorder, MECP2 Duplication syndrome and Prader-Willi syndrome, as well as Down syndrome, autism and cerebral palsy which occur more frequently. Jenny has used cohort, observational and qualitative study designs to progress these research fields and her expertise in these rare disorders is being recognised internationally. She works with consumers to develop meaningful research programs and aims for the translation of research findings into clinical practice. She has a strong vision of what success looks like for both children and their families which, over the short and long term, includes living with a strong quality of life.

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