Developing a dementia-specific health state classification system for a new preference-based instrument AD-5D

Abstract

BackgroundWith an ageing population, the number of people with dementia is rising. The economic impact on the health care system is considerable and new treatment methods and approaches to dementia care must be cost effective. Economic evaluation requires valid patient reported outcome measures, and this study aims to develop a dementia-specific health state classification system based on the Quality of Life for Alzheimer’s disease (QOL-AD) instrument (nursing home version). This classification system will subsequently be valued to generate a preference-based measure for use in the economic evaluation of interventions for people with dementia.MethodsWe assessed the dimensionality of the QOL-AD to develop a new classification system. This was done using exploratory and confirmatory factor analysis and further assessment of the structure of the measure to ensure coverage of the key areas of quality of life. Secondly, we used Rasch analysis to test the psychometric performance of the items, and select item(s) to describe each dimension. This was done on 13 items of the QOL-AD (excluding two general health items) using a sample of 284 residents living in long-term care facilities in Australia who had a diagnosis of dementia.ResultsA five dimension classification system is proposed resulting from the three factor structure (defined as ‘interpersonal environment’, ‘physical health’ and ‘self-functioning’) derived from the factor analysis and two factors (‘memory’ and ‘mood’) from the accompanying review. For the first three dimensions, Rasch analysis selected three questions of the QOL-AD (‘living situation’, ‘physical health’, and ‘do fun things’) with memory and mood questions representing their own dimensions. The resulting classification system (AD-5D) includes many of the health-related quality of life dimensions considered important to people with dementia, including mood, global function and skill in daily living.ConclusionsThe development of the AD-5D classification system is an important step in the future application of the widely used QOL-AD in economic evaluations. Future valuation studies will enable this tool to be used to calculate quality adjusted life years to evaluate treatments and interventions for people diagnosed with mild to moderate dementia.

Confirmatory analysis of a health state classification system for people living with dementia: a qualitative approach

“…Results from the three focus groups confirmed that the important aspects of quality of life for people with dementia could be organized into five domains, thereby supporting the results of the previous factor analysis of the QOL-AD. 9 This confirmatory analysis was important to allow a relatively simplified version of the QOL-AD health states to be presented for valuation.…”

“…Psychometric analyses previously conducted to develop a dementia-specific health state classification system based on the QOL-AD 9 identified five domains that could be used to develop QALYs for dementia: physical health, mood, memory, living situation and ability to do things for fun. These domains were explained and participants were asked to assign the identified activities to a domain.…”

“…7 More recently, preference-based scoring algorithms (the DEMQOL-U and DEMQOL-Proxy-U) have been developed for the DEMQOL to facilitate its application in this context. 8 In 2016, Nguyen et al 9 conducted factor and Rasch analyses on the 13-item nursing home version of the QOL-AD that identified five core domains that were important for the health-related quality of life of people living with dementia (the Alzheimer's diseasefive dimensions or AD-5D): memory, mood, living situation, physical health and ability to do things for fun. 9 This analysis laid the groundwork for a larger study to develop preference-based utility weights for the AD-5D to enable its use in economic evaluation of interventions for people with dementia.…”

How do people with dementia and family carers value dementia‐specific quality of life states? An explorative “Think Aloud” study

“…Recent acknowledgement of these types of limitations has motivated the development of the DEMQOL‐U, a dementia‐specific preference‐based instrument generated from the DEMQOL . A new dementia‐specific quality of life classification system, the Alzheimer's Disease Five Dimensions (AD‐5D), has also recently been developed, based upon the Quality of Life in Alzheimer's Disease (QOL‐AD), a widely used and well‐validated condition‐specific instrument for assessing health‐related quality of life for people living with dementia …”

Developing a dementia-specific preference-­based quality of life measure (AD-5D) in Australia: a valuation study protocol

“…Our team has recently developed a new health state classification system, the alzheimer’s disease five dimensions (AD-5D) 25 based on the QOL-AD nursing home version. 26 The QOL-AD, originally developed for people with dementia living in the community, 27 is the quality of life measure for people with dementia recommended in European guidelines due to its brevity, validity and wide usage.…”