Genetic test might one day diagnose the disease before symptoms occur, researchers say
FRIDAY, Sept. 29, 2017 (HealthDay News) -- A new test that checks for multiple gene variants linked with Alzheimer's disease may be more effective than testing for a single genetic variant, a new study suggests.
The genetic variant APOE E4 is regarded as the strongest genetic predictor of whether a person is likely to develop the memory-robbing disease. But it's present in only 10 to 15 percent of people. And recent research suggests its impact has been overestimated, the study authors said.
They developed a test that estimates the risk of Alzheimer's in the 85 to 90 percent of people who don't have at least one copy of APOE E4 but still have other gene variants that put them at risk of Alzheimer's. The test is called the polygenic hazard score (PHS).
The researchers reviewed five years of data from nearly 1,100 Americans without dementia. They concluded that the new test could predict how long it would take the study participants to progress to Alzheimer's disease and the speed of their mental decline.
"Beyond APOE E4 by itself, our polygenic hazard score can identify cognitively normal and mildly impaired older folks who are at greatest risk for developing Alzheimer's-associated clinical decline over time," said study first author Chin Hong Tan. A postdoctoral scholar at the University of California, San Francisco, Tan made the comments said in a school news release.
Autopsies on people who had Alzheimer's found that a higher PHS was associated with more Alzheimer's-related amyloid plaque in the brain. These people also reportedly had faster declines on tests of mental skills while living.
Older people with the highest PHS had the highest rates of Alzheimer's, regardless of their APOE E4 status, the study authors said.
"Our findings have strong implications for [research] trials in Alzheimer's, as well as direct-to-consumer genetic tests, some of which have recently received FDA clearance," said study co-author Anders Dale, a professor of neurosciences and radiology at the University of California, San Diego.
The study was published recently in the Annals of Neurology.
The U.S. National Institute on Aging has more about Alzheimer's disease.