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

Area of Science:

• Gerontology
• Health Economics
• Psychometrics

Background:

• The rising prevalence of dementia necessitates cost-effective care and treatment strategies.
• Economic evaluations require valid patient-reported outcome measures.
• The Quality of Life for Alzheimer's disease (QOL-AD) instrument is widely used but requires a dementia-specific classification system for economic evaluation.

Purpose of the Study:

• To develop a dementia-specific health state classification system based on the QOL-AD instrument.
• To create a preference-based measure for economic evaluations of dementia interventions.
• To ensure the classification system captures key quality of life dimensions relevant to people with dementia.

Main Methods:

• Assessed QOL-AD dimensionality using exploratory and confirmatory factor analysis.
• Employed Rasch analysis to test psychometric performance and select items for each dimension.
• Utilized data from 284 Australian long-term care residents with dementia.

Main Results:

• A five-dimension classification system (AD-5D) was developed, incorporating 'interpersonal environment', 'physical health', 'self-functioning', 'memory', and 'mood'.
• Specific QOL-AD items were selected to represent 'living situation', 'physical health', 'do fun things', 'memory', and 'mood'.
• The AD-5D system includes crucial dimensions such as mood, global function, and daily living skills.

Conclusions:

• The AD-5D classification system facilitates the use of the QOL-AD in economic evaluations.
• Future valuation studies will enable the AD-5D to calculate quality-adjusted life years for mild to moderate dementia.
• This tool supports the economic assessment of interventions for dementia care.