A review of quality of life in Alzheimer's disease. Part 2: Issues in assessing drug effects.

There are numerous methods available for assessing patients with Alzheimer's disease (AD) or other forms of dementia. Quality-of-life (QOL) assessment is unique among these methods. The subjective nature of quality of life provides healthcare professionals with the opportunity of incorporating the value systems of patients and their carers into their assessments. A systematic review was carried out to assess the published data (and some unpublished data) on QOL assessment tools and instruments that claim to measure quality of life in dementia. A number of measures or methods used in the literature for assessing the quality of life of patients with dementing illnesses were identified. It was decided to present the resultant review in 2 parts that correspond to the 2 main groups into which the instruments were categorised. The first (part 1), looked at measures used to assess the impact of disease as well as instruments at a developmental or testing stage. The second (part 2), includes instruments that claim to measure quality of life in studies documenting the impact of a drug in this therapeutic area. This second group consists mainly of instruments identified as being used to assess quality of life during clinical trials in dementia/AD. As in part 1, this part of the review was unable to identify any validated methods of assessing the quality of life of both patients with dementia and their carers at the same time. The ideal instrument must show that it can reliably, reproducibly and comprehensively assess quality of life for both patients with dementia and their carers. It should also demonstrate that it can measure quality of life effectively using a practical administration technique that does not place any unnecessary burden on either informal carers, other healthcare workers involved or the patient themselves. In addition, any measure intended for use in assessing the impact of drug treatment on quality of life must demonstrate sensitivity to change, also known as responsiveness. All these criteria are even more important when measuring quality of life as an outcome during clinical trials of a new antidementia drug, because the data generated are likely to influence decisions made by regulatory bodies about whether to grant licences that are required by pharmaceutical companies to market their products. Further cross-sectional and longitudinal research is required to ensure that the available instruments possess the essential psychometric criteria that must be demonstrated prior to their utilisation in clinical trials of any compound developed for use in dementia/AD. Ongoing conceptual research may still be useful in exploring new ways of assessing quality of life in this important therapeutic area.