Clinical Lab Manager
The only sure way to confirm Alzheimer's remains an autopsy of the brain after death, but studies suggest that emerging biomarkers may eventually provide a reliable way to confirm the disease in living patients. In a review of biomarker studies, published in April 2020 in Annals of Internal Medicine, researchers concluded that three different tests are highly accurate at distinguishing between Alzheimer's disease and other causes of dementia. Studies compared diagnoses from these tests to autopsy results after death to confirm the presence or absence of Alzheimer's.
The first highly accurate test was an amyloid positron emission tomography (PET) scan, which involves injecting patients with a radioactive substance and then measuring the radiation emitted. In amyloid PET, clinicians can map the build-up of amyloid protein with greater than 90 percent diagnostic accuracy. The second test was fluorodeoxyglucose- (FDG) PET, which uses fluorodeoxyglucose to map how the brain is absorbing glucose. FDG-PET could accurately detect the disease about 90 percent of the time. The third test was magnetic resonance imaging (MRI). Clinicians can use MRI to detect size changes in the temporal lobe of the brain, with reduced volume of the hippocampus indicating Alzheimer's. The accuracy of MRI diagnosis was greater than 90 percent.
The researchers say that while these tests show promise to improve the diagnosis of Alzheimer's disease, variation in the studies' methods and subjects means test accuracy in a clinical setting would most likely be lower. Biomarker testing also requires more standardization to set measurement levels and test methods, they say.