Study designs of evaluations included in the review
Diagnostic accuracy studies that included at least 12 patients with AD were eligible for inclusion.
Specific interventions included in the review
Studies of FDG PET in which a dedicated scanner was used and the resolution was reported were eligible for inclusion. The included studies used a range of different scanners. The criteria for positivity also varied and included: frontoparietal hypometabolism; symmetrical parietotemporal hypometabolism; hypometabolism index; any hypometabolism; parietotemporal hypometabolism; metabolic ratio; any deficit; out of mean +/- 2 standard deviations; and parietotemporal and frontal hypometabolism.
Reference standard test against which the new test was compared
Studies in which the reference standard for the diagnosis of AD was either a clinical diagnosis according to standard criteria of the National Institute of Neurological and Communicative Disorders/Alzheimer's Disease and Related Disorders Association or the Diagnostic and Statistical Manual, or histopathological diagnosis were eligible for inclusion. All studies used clinical examination to diagnose dementia; some studies also used histopathological diagnosis after a period of follow-up in all or some of the included patients.
Participants included in the review
Studies that included patients with AD defined using standard criteria were eligible for inclusion. Most of the studies were conducted in tertiary care settings. Patients classified having AD included those with probable disease, possible disease, mild dementia, moderate dementia, severe dementia and mild cognitive impairment. Patients classified as controls included healthy controls, patients with multi-infarct dementia, dementia with Lewy bodies, dementia not caused by AD, questionable or mild dementia, and vascular dementia.
Outcomes assessed in the review
Studies had to provide sufficient data to construct a 2x2 table of test performance. The outcomes reported in the review were the sensitivity and specificity.
How were decisions on the relevance of primary studies made?
Two reviewers, one methodologist and one content expert, reviewed the abstracts of all studies identified by the searches. Studies considered relevant by at least one reviewer were obtained. Two reviewers then independently reviewed the full-text articles; any disagreements were resolved through consensus.