Alzheimer disease: operating characteristics of PET--a meta-analysis

To assess the operating characteristics of positron emission tomography (PET) by using fluorine 18 fluorodeoxyglucose (FDG) in the diagnosis of Alzheimer disease.

Articles published between 1989 and 2003 were identified in the MEDLINE, CINAHL, and HealthSTAR databases. Articles were selected if FDG PET was performed with a dedicated scanner and the resolution was specified, if standard criteria were used for the diagnosis of Alzheimer disease, if at least 12 human subjects with Alzheimer disease were enrolled in the study, if clinical diagnosis or histopathologic findings were used as the reference standard, and if sufficient data were provided to construct a 2 x 2 table. Two reviewers independently abstracted data regarding the operating characteristics (sensitivity and specificity) of PET and evaluated the study quality. A meta-analysis was performed by constructing a summary receiver operating characteristic curve and by combining the sensitivity and specificity values by using a random-effects model.

Fifteen articles that met the inclusion criteria showed heterogeneity in sensitivity and specificity estimates that were not related to quality features with no plausible explanations. The summary sensitivity of PET was 86% (95% CI: 76%, 93%), and the summary specificity was 86% (95% CI: 72%, 93%).

The specificity and sensitivity of FDG PET are limited by both study design and patient characteristics. Therefore, the clinical value of these parameters is uncertain; future research on the use of PET in the diagnosis of Alzheimer disease needs to focus on current limitations to be of practical relevance in clinical settings.