While PET scans of the brain are the most widely accepted method for detecting Alzheimer’s disease before symptoms appear, they typically cost $4,000. Researchers from Washington University School of Medicine in St. Louis have worked on developing a more efficient test, a blood test to detect amyloid proteins that could be given to thousands of people per month at a much lower cost, reported Arlene Weintraub in Fierce Biotech.
At first, they created a test designed to detect small amounts of amyloid in the blood. Because it was accurate only 88 percent of the time when compared to PET images, they combined the blood test with two other major risk factors for the disease: age and the presence of the APOE4 gene variant. That increased the accuracy of the test to 94 percent, they wrote in the journal, Neurology. While gender is also a risk factor in that 2/3 of Alzheimer’s patients are women, putting that in the analysis did not improve the accuracy of the test.
The study included 158 people over the age of 50, all but 10 of whom did not show any signs of cognitive decline when they enrolled. The scientists used mass spectrometry for measuring the ratio of amyloid beta 42 and amyloid beta 40 in the blood. That ratio decreases when deposits of the protein are growing in the brain.
Additionally, the researchers studied the false positives, the blood tests that had indicated the presence of amyloid even when brain scans revealed no signs of Alzheimer’s. In some of those patients, when PET scans were performed later, early signs of amyloid deposits were found, showing that the blood test might help to detect Alzheimer’s long before symptoms appear.
Other researchers have said that measuring the ratio of amyloid beta 42 and 40 in blood could help to detect Alzheimer’s. Eisai, which is working on a prototype blood test to do that, reported that it had found a strong correlation between the ratios of the two types of protein in both blood and cerebral spinal fluid taken from asymptomatic people and those with mild cognitive impairment. Eisai and its partner, Sysmex, are planning to compare the results with PET images.
While there have been some notable failures in the field, the quest for effective Alzheimer’s treatments continues. Amgen and Novartis recently stopped trials of a BACE inhibitor after some patients had worsening cognitive impairment, but many clinical trials for other treatments aimed at treating or preventing the disease are underway. That is where an effective blood test for early detection could come in handy, according to the University of Washington researchers.
Senior author and Washington University neurology professor Randall Bateman, M.D., explained, "If you want to screen an asymptomatic population for a prevention trial, you would have to screen, say, 10,000 people just to get 1,500 or 2,000 that would qualify. Reducing the number of PET scans could enable us to conduct twice as many clinical trials for the same amount of time and money.”
The research team included a financial analysis based on records from an Alzheimer’s prevention trial using PET scans to confirm changes in the brain that would indicate the onset of Alzheimer’s. Had those patients been prescreened with a blood test, it would have decreased the number of PET scans needed by about 60 percent, the Washington University researchers concluded.