The most widely accepted method for detecting Alzheimer’s disease before symptoms arise is to take a PET scan of the brain, to search for the amyloid protein deposits that are a hallmark of the disease. Scientists from Washington University School of Medicine in St. Louis set out to develop a more efficient test—a blood test.
The first test they developed, which was designed to detect tiny amounts of amyloid in the blood, was accurate only 88% of the time when compared to PET images. Next, they tried combining the blood test with two other major risk factors for Alzheimer’s: age and the presence of the APOE4 gene variant.
The study involved 158 people over the age of 50, all but 10 of whom showed no signs of cognitive decline when they enrolled. The researchers used mass spectrometry to measure the ratio of amyloid beta 42 and amyloid beta 40 in the blood, because that ratio is known to drop when deposits of the protein are increasing in the brain. The accuracy of the test rose to 94%, said the researchers.
As part of their analysis, the researchers went back to study the false positives—the blood tests that initially showed the presence of amyloid even when brain scans showed no signs of Alzheimer’s. In some of those patients, when PET scans were repeated an average of four years later, early signs of amyloid deposits were detected. This could be early proof that the blood test may be useful for detecting Alzheimer’s long before symptoms appear, the researchers suggested in a statement.
The search for effective Alzheimer’s treatments continues, and with the many clinical trials underway for new treatments aimed at treating or preventing the disease, an effective blood test for early detection could prove useful.
Source: FierceBiotech, August 1, 2019