AILSA CHANG, HOST:
A new generation of blood tests promises to change the way doctors diagnose and treat Alzheimer's disease. But there is a snag. Tests have arrived so quickly that there's little guidance on who should get them or how to interpret the results. NPR's Jon Hamilton reports from the Alzheimer's Association International Conference in Philadelphia.
CHANG: A new generation of blood tests promises to change the way doctors diagnose and treat Alzheimer's disease. But there is a snag. Tests have arrived so quickly that there's little guidance on who should get them or how to interpret the results. NPR's Jon Hamilton reports from the Alzheimer's Association International Conference in Philadelphia.
JON HAMILTON, BYLINE: The blood tests show whether a person with memory and thinking problems also has Alzheimer's. Dr. Suzanne Schindler of Washington University in St. Louis says just a few months ago, many of these tests were still unreliable.
SUZANNE SCHINDLER: Blood tests have developed incredibly fast for Alzheimer disease, and I think people aren't used to that rate of change.
HAMILTON: The tests indicate sticky amyloid plaques and tangled fibers called tau in the brain, the hallmarks of Alzheimer's. Until now, finding these has meant getting an uncomfortable spinal tap or a costly PET scan. But Schindler says that's changing, thanks to blood tests that look for an abnormal protein called p-tau217.
SCHINDLER: When you're just looking at cognitively impaired individuals like you might be seeing in a clinic, these p-tau217 tests perform very well.
HAMILTON: They're right about 90% of the time. Several p-tau217 tests are commercially available, though none is approved by the Food and Drug Administration. And Schindler says the tests are being ordered by more and more doctors and not just specialists.
SCHINDLER: Physicians really need to educate themselves about these tests because this is coming, and this is coming really soon.
HAMILTON: One major reason is the approval of two drugs that can slow down Alzheimer's. These drugs are available only to people with confirmed amyloid plaques in the brain. Dr. Eliezer Masliah of the National Institute on Aging says the rise of blood testing reflects a larger shift in the Alzheimer's field.
ELIEZER MASLIAH: The trend now is to go toward a biological diagnosis of Alzheimer disease; that is, a diagnosis based on biomarkers rather than just on clinical symptoms.
HAMILTON: Biomarkers like p-tau217. And Masliah says new markers are being discovered all the time.
MASLIAH: All this really points to this idea of, OK, now we're going to use a blood test to diagnose Alzheimer disease, and I think we are very close to that.
HAMILTON: Yet many primary care doctors don't yet know how and when to use this new tool, says Dr. Heather Whitson of Duke University.
HEATHER WHITSON: The field is moving at a pace that I never imagined 10 years ago.
HAMILTON: Whitson says physicians should reserve the tests for patients with clear signs of impairment - for example, someone who asks the same question repeatedly during a visit and often forgets to take medications at home. But she says the tests aren't for people who are just anxious about their brain health.
WHITSON: So they'd sometimes struggle to remember a name or a place, but maybe they have a family history of Alzheimer's disease. So every time they forget a name, they're worried that this is it.
HAMILTON: These patients aren't eligible for drug treatment, and Whitson says a positive test might cause needless anxiety.
WHITSON: A percentage of the population has amyloid in their brain, and they will live out a normal lifespan and never have symptoms. We know this.
HAMILTON: Experts at the Alzheimer's conference say that within a few years, it's likely that primary care doctors will be offering blood tests to many of their older patients with memory problems, and they'll know what to do when a test is, say, borderline rather than positive or negative. But Dr. Howard Fillit of the Alzheimer's Drug Discovery Foundation says getting a diagnosis is just the first step.
HOWARD FILLIT: What does it mean for the family? What does it mean for the spouse? This is a huge effect. And the primary care doctor can make the diagnosis. The question is, will they spend the hour that's needed to do the education and counseling?
HAMILTON: And will payers like Medicare cover those services? Jon Hamilton, NPR News.
(SOUNDBITE OF MUSIC) Transcript provided by NPR, Copyright NPR.
NPR transcripts are created on a rush deadline by an NPR contractor. This text may not be in its final form and may be updated or revised in the future. Accuracy and availability may vary. The authoritative record of NPR’s programming is the audio record.
