New tests of blood and spinal fluid can show how far Alzheimer’s has progressed and how fast a patient’s memory will decline.
MARY LOUISE KELLY, HOST:
New tests of blood and spinal fluid can identify people experiencing memory loss from Alzheimer’s disease. NPR’s Jon Hamilton reports that the experimental tests could eventually help doctors diagnose the disease and could predict which patients will benefit from drug treatment.
JON HAMILTON, BYLINE: Current blood tests can show whether a person’s brain contains the sticky amyloid plaques associated with Alzheimer’s disease. But Dr. Randall Bateman of Washington University in St. Louis says that’s not the whole story.
RANDALL BATEMAN: People are walking around with amyloid plaques in their brains and their brains are adapting to it and making do, but they don’t have any symptoms of it.
HAMILTON: And some never will, so Bateman and his team were excited when they found a protein fragment in spinal fluid that did indicate cognitive problems.
BATEMAN: It was much more related to memory loss, symptom onset, dementia stage – all the things that patients care about.
HAMILTON: The protein fragment, called MTBR-tau243, isn’t associated with amyloid plaques. Instead, it is closely linked to the other hallmark of Alzheimer’s – tangled fibers that build up inside neurons. And Bateman says this particular fragment rises when tangles begin affecting neurons.
BATEMAN: It only goes up when people are symptomatic. So you can look at people who are – have a headful of amyloid, and if they don’t yet have dementia, memory loss, the symptoms of Alzheimer’s, it’s still negative.
HAMILTON: Until now, the test for the protein fragment has required a spinal tap, which limited its use in clinical trials. But in a new study, Bateman’s team shows that the test works on blood samples, too. He says that means doctors should soon have an easy way to tell whether the amyloid plaques in a patient’s brain are actually affecting memory and thinking.
BATEMAN: We can now make a much more informed choice about how much benefit are you likely to get if we undergo a treatment to remove the amyloid plaques and balance that with – what is the risk?
HAMILTON: The tau243 study, funded by the National Institutes of Health, appears in the journal Nature Medicine. A second study in the same journal offers a different way to assess and even predict the memory loss associated with Alzheimer’s. Tony Wyss-Coray of Stanford University says his team set out to answer a simple question related to aging.
TONY WYSS-CORAY: Can we find proteins that change if a person’s memory is not working well?
HAMILTON: With NIH funding, the team studied more than 7,000 proteins in the spinal fluid of more than 3,000 people, and Wyss-Coray says two proteins stood out. One rose dramatically in people with memory problems, the other fell sharply.
WYSS-CORAY: So we made a ratio between the two, and that ratio turns out to be a very good indicator of whether a person’s memory is OK or not.
HAMILTON: Wyss-Coray says they use the sample to assess spinal fluid samples from people who have a genetic predisposition to Alzheimer’s.
WYSS-CORAY: In these individuals, it goes up 10 to 20 years before they get the actual disease diagnosis correlating with their subtle impairment of cognition.
HAMILTON: Both proteins in the test are involved in maintaining synapses, the connections between neurons. So Dr. Paul Worley of Johns Hopkins University says it makes sense that levels of these proteins change when Alzheimer’s begins to affect brain function.
PAUL WORLEY: The exciting thing here is that this is a process that seems to anticipate the development of cognitive decline 10, 20, 30 years later.
HAMILTON: Worley says that sets the stage for Alzheimer’s treatments that begin long before symptoms appear, and he predicts that future treatments will include drugs that target the brain synapses. Jon Hamilton, NPR News.
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