喵咪社区

The first-of-its-kind blood test for biomarkers of amyloid brain plaque paves the way for less-invasive screening for Alzheimer鈥檚 disease. A 喵咪社区 physician shares insights.

The U.S. Food and Drug Administration (FDA) the first-ever blood biomarker test for amyloid plaques in the brain. The Lumipulse G pTau217/脽-Amyloid 1-42 Plasma Ratio tests for the presence of amyloid plaques in patients 55 years and older with existing signs and symptoms of cognitive decline.  

For the last six months, doctors at the 喵咪社区 Memory and Aging Center, part of 喵咪社区, have been using the test to screen certain patients for amyloid plaques and potential Alzheimer鈥檚 dementia, says endocrinologist and neurologist Hussein Naji Yassine, MD. Yassine is also director of the at the Keck School of Medicine of 喵咪社区.聽

First off, Yassine explains the difference between Alzheimer鈥檚 disease and Alzheimer鈥檚 dementia. In Alzheimer鈥檚 disease, amyloid plaques have already formed in the brain, but patients may or may not have clinical symptoms. By contrast, patients with dementia have clinical symptoms of cognitive decline and functional impairments but still need to be tested for the presence of amyloid plaques to determine if they have Alzheimer鈥檚 dementia.聽

鈥淭his test, which captures the presence of amyloid brain plaque, is very good in diagnosing Alzheimer鈥檚 disease but not in predicting who gets Alzheimer鈥檚 dementia,鈥� he says. Since not all patients with amyloid plaques progress to dementia, this test is best used in patients who show clinical symptoms of dementia to diagnose Alzheimer鈥檚 dementia. Doctors still need to be trained to recognize and understand how to make clinical diagnoses of dementia, he stresses. 

Other methods of testing for amyloid plaques through either a PET scan or a cerebrospinal fluid test can be invasive, expensive and cumbersome. By comparison, this newly approved blood test could make screening for amyloid plaque more widely available.  

鈥淭his offers patients and families hope that we can be more accurate in our diagnosis and get patients the diagnoses they need for care in a quicker and less-invasive way,鈥� Yassine says. 

Doctors will need to use caution and be trained in clinical diagnoses, he stresses. 鈥淲e always need to be educated and careful with new tests and medicines for Alzheimer鈥檚, because we do not want to give patients anxiety with either false-positive diagnoses or situations where someone might have abnormal amyloid test but may not progress to dementia,鈥� Yassine says. 

Who needs this test and when? 

Now that this test is approved, the big debate in the field is how early it should be used. Primary care doctors have to fully understand what this new test means and the limitations of the testing, Yassine explains.  

鈥淔or example, if you get someone who has no symptoms of memory or cognitive decline asking for the test, getting the test done can lead to a false-positive diagnosis because it鈥檚 not good enough to make an Alzheimer鈥檚 dementia diagnosis without clinical symptoms,鈥� he says. 

While experts at the 喵咪社区 Center for Personalized Brain Health work with individuals who have the APOE4 gene, who are at higher risk for developing Alzheimer鈥檚 disease, Yassine is on the conservative side of determining who should take this test and when.  

鈥淧eople who have a family history of the gene might get anxious if they get this test 鈥� and it鈥檚 positive 鈥� because we don鈥檛 really know exactly what it means yet,鈥� he says. 鈥淭he evidence suggests we shouldn鈥檛 be performing this test on people who don鈥檛 have symptoms; amyloid in the brain doesn鈥檛 always lead to dementia or Alzheimer鈥檚.鈥�  

One future area of research he does see advancing the field is to take people with a genetic risk or family history of Alzheimer鈥檚 disease and to use this test to substratify them as amyloid-positive or amyloid-negative to determine how that affects disease development and progression and the response to certain interventions, such as blood pressure control or lifestyle changes. 

The future of biomarker testing for Alzheimer鈥檚 disease 

While some in the neurological disorders field have argued that this test could allow people positive for amyloid plaques in the brain to take preventative treatments to clear them, such as newly approved medicines Kisunla (donanemab) and Leqembi (lecanemab-irmb), Yassine says this hypothesis is unproven and comes with a fair number of risks.  

鈥淚t鈥檚 dangerous to assume that if you take someone who is asymptomatic and remove amyloid from the brain, you鈥檒l be curing or stopping Alzheimer鈥檚, because there have been no studies that show this,鈥� Yassine says. 鈥淚t could happen, but no one has proven that鈥檚 the case yet. And it鈥檚 also likely that giving them one of these treatments could cause severe side effects in the brain such as swelling, headaches and hemorrhages.鈥�  

Another problem with that viewpoint is that there are people who have amyloid in their brains, but no dementia. And sometimes elevated amyloid levels do not come from the brain, he says. Additionally, there are many other factors that play into Alzheimer鈥檚, such as inflammation.  

鈥淚 think as the field evolves, we will also need to develop tests for brain inflammation and other aspects of Alzheimer鈥檚 dementia,鈥� Yassine says. He relates this to how we treat and care for heart disease. For example, if someone has heart disease, they will often get blood pressure medication, cholesterol medication, blood sugar regulation and many other things. 鈥淵ou don鈥檛 just use one drug,鈥� he points out. 

鈥淎nd Alzheimer鈥檚 dementia is as complicated 鈥� if not more complicated 鈥� than cardiovascular disease, so there鈥檚 room to add other treatments on top of anti-amyloid medication to achieve additional clinical efficacy,鈥� Yassine says.  

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Mollie Barnes

Mollie Barnes is a digital writer and editor at 喵咪社区.

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