Fluorodeoxyglucose-positron-emission tomography, single-photon emission tomography, and structural MR imaging for prediction of rapid conversion to Alzheimer disease in patients with mild cognitive impairment: a meta-analysis.

Patients with mild cognitive impairment (MCI) are at risk for developing Alzheimer disease (AD). To diagnose AD at an early stage, one must develop highly specific and sensitive tools to identify it among at-risk subjects. The purpose of this study was to evaluate and compare the ability of fluorodeoxyglucose-positron-emission tomography (FDG-PET), single-photon emission tomography (SPECT), and structural MR imaging to predict conversion to AD in patients with MCI. Relevant studies were identified with MEDLINE from January 1990 to April 2008. Meta-analysis and meta-regression were done on the diagnostic performance data for each technique from eligible studies. We estimated and compared the weighted summary sensitivities, specificities, likelihood ratios (LRs), and summary receiver operating characteristic curves of each imaging technique. Twenty-four eligible studies were included, with a total of 1112 patients. FDG-PET performed statistically better in LR+ and odds ratio (OR), whereas no statistical difference was found in pooled sensitivity, specificity, and LR- for each technique. No statistical difference was confirmed between SPECT and MR imaging. The Q* index estimates for FDG-PET, SPECT, and structural MR imaging were respectively 0.86, 0.75, and 0.76. In meta-regression, statistical significance was found only between technique and log OR, with a regression coefficient of -0.575. This meta-analysis showed that FDG-PET performs slightly better than SPECT and structural MR imaging in the prediction of conversion to AD in patients with MCI; parallel performance was found between SPECT and MR imaging.