When should functional neuroimaging techniques be used in the diagnosis and management of Alzheimer's dementia? A decision analysis.

Background: Functional neuroimaging, including positron emission tomography (PET), has been proposed for use in diagnosing Alzheimer's disease-related dementia (AD).

Objective: The objective of this study was identify the circumstances under which PET scanning for the diagnosis of AD maximizes health outcomes.

Methods: A Markov-model-based decision analysis was conducted using estimates derived from the literature on AD epidemiology, the accuracy of PET, and donepezil treatment efficacy. The target population for the analysis was assumed to be US men and women who either have mild AD or are asymptomatic but at an elevated risk of developing AD owing to disease in a first-degree relative (parent or sibling). The time horizon was the patient lifetime. We compared treatment 1) based on an American Academy of Neurology (AAN) clinical evaluation either alone; 2) in combination with PET scanning; or 3) empirically based on a family history. Outcomes measures were life expectancy, quality-adjusted life-years (QALYs), and (severe) dementia-free life expectancy (SDFLE).

Results: For both patient populations, treating all patients based on an AAN evaluation without further testing using PET resulted in the greatest gains in life expectancy, QALYs, and SDFLEs. PET-based testing was the second preferred strategy compared to no intervention. The rankings of the strategies were sensitive to severity of treatment complications: analyses of hypothetical treatments with the potential for severe complications indicated that testing was preferred if the treatment was effective but had moderate complications.

Conclusions: These results suggest that current treatments, which are relatively benign and may slow progression of disease, should be offered to patients who are identified as having AD based solely on an AAN clinical evaluation. A clinical evaluation that includes functional neuroimaging based testing will be warranted, however, when new treatments that are effective at slowing disease progression but have the potential for moderate to severe complications become available.