Purpose: Growing evidence indicates that appropriate incorporation of positron emission tomography (PET) into the evaluation of patients with early symptoms of cognitive decline can improve diagnostic and prognostic accuracy. In the present work, an explicitly defined role for PET and its associated impact on expected clinical outcomes were systematically examined.
Procedures: We compared the relative value of two strategies for assessing whether Alzheimer's disease (AD) was responsible for cognitive decline in geriatric patients, and in subsequently managing those patients according to the recommended standards of the American Academy of Neurology (AAN). The first strategy was based on an approach already endorsed by the AAN, following evidence-based reviews carried out by its quality standards subcommittee. The second approach was based on many of the same AAN recommendations-with respect to initial general medical and neurologic examination, structural imaging and laboratory tests, as well as ultimate management-but additionally incorporated PET in appropriate cases, to determine the presence or absence of a pattern of regional cerebral metabolism characteristic of AD. Clinical outcomes accruing to each strategy were calculated using formalized tools of decision analysis.
Results: The strategy making use of PET increased diagnostic accuracy, yielding decreased rates of both false negative (from 8.3 to 3.1%) and false positive (from 23.0 to 11.9%) diagnoses for AD, compared with the conventional strategy. When coupled with AAN treatment recommendations for patients having (or not having) non-severe AD, these differences in diagnostic accuracy corresponded to approximately a 62% decrease in avoidable months of nursing home care, and a 48% decrease in months of unnecessary drug therapy resulting from inaccurate diagnoses. The benefit in clinical outcome of the proposed strategy was maintained over a wide range of values for sensitivity, specificity, and projected impact on need for nursing home care.
Conclusion: Use of PET for evaluating early cognitive decline in geriatric patients can add valuable information to the clinical assessment, resulting in a greater number of patients being accurately diagnosed and properly treated. PET can be used to diminish disease-related and treatment-related morbidity of dementia, through earlier institution of appropriate management.