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Amyloid PET scan

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Amyloid PET A scans can detect amyloid-beta plaques, acore neuropathological feature of Alzheimer’s disease.

The diagnosis of Alzheimer’s disease and related disorders are based on clinical criteria, but has limited sensitivity and specificity compared with autopsy.

The addition of the amyloid PET scan to the clinical assessment enhances diagnostic accuracy.

Three amyloid-beta tracers-fluorine 18 labeled florbetapir, F-labeled flutemetamol, and F-labeled florbetaben have been approved.

With an Amyloid PET Imaging study it is possible to examine the brains of living patients to determine whether amyloid plaques, a key Alzheimer’s disease pathology, are present.

Prior to amyloid PET imaging AD was diagnosed primarily through an evaluation of a patient’s cognitive symptoms in combination with blood and non-PET imaging tests to rule out causes of cognitive decline other than AD.

The FDA has approved several different tracers that bind to beta-amyloid in the brain and can reveal amyloid plaques during a PET scan.

PET imaging has helped to demonstrate that amyloid plaques begin accumulating in the brain up to 15 years before the earliest signs of memory loss begin to manifest, allowing the potential to diagnose patients at significantly earlier stages of disease.

PET scans have shown that many people previously diagnosed with AD do not actually have amyloid plaques and therefore do not have AD.

False-positive diagnoses may well be as high as 20%.

AD is defined by the accumulation of both beta-amyloid plaques and neurofibrillary tangles in the setting of cognitive decline, but PET scans currently detect only plaques.

The only alternative method of identifying amyloid plaques in the brain is via a lumbar puncture, measuring cerebral spinal fluid for amyloid-beta protein.

Lumbar punctures and amyloid PET imaging provide very complementary results, agreeing between 85% and 90% of the time.

PET to autopsy studies in end-of-life patients revealed an 89-98% sensitivity and 80%-895% specificity for detecting any moderate-frequent neuritic amyloid plaques at autopsy.

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