Quantifying health status in dementia

As disease-modifying medications become available for Alzheimer’s disease and other types of dementia, evaluation instruments play a key role in assessing treatment efficacy and efficiency. Therefore, patient reported outcomes and caregiver reported outcomes on the health status or health-related quality of life (HRQoL) of dementia patients are important outcome measures. The purpose of this study is to develop a novel HRQoL measurement instrument that is particularly devised for use in the area of dementia. This instrument will combine the advantages of disease-specific and value-based HRQoL instruments. Presently, such an instrument is absent in the field of dementia. As a first step a HRQoL classification for dementia will be developed: the Dementia Quality of life Classification (DQC). This will be done in analogy to a widely applied existing generic value-based HRQoL instrument, the EQ-5D. Similar to the EQ-5D the DQC instrument will comprises five health domains relevant for dementia, each with 3 levels. The next step is to derive an algorithm for the DQC, which enables to attach meaningful overall numeric measures with sufficient precision to each possible DQC state. Our planned valuation study will be based on the modern framework of discrete choice models. An informative set of 60 pairs of DQC health states will be constructed using a Bayesian approach. The discrete choice tasks will be programmed as a web-based computer experiment which will be judged by a representative sample of the Dutch population (N = 600). To validate these responses, workers in the field of dementia will be contacted to judge the same set of DQC health states. Subsequently, the data generated in the discrete choice experiment will be used as input for a statistical model to estimate the levels of the five domains. Specific scaling issues related to the anchors of the instrument will also be addressed.