VOA新闻杂志2024--Researchers: New Blood Tests Help Doctors Identify Alzheimer's Disease

New blood tests could help to identify, or diagnose, Alzheimer's disease faster and with more accuracy, researchers reported recently. However, some of the tests for the brain-wasting disease appear to work better than others.

New tests, new drugs

Doctors can confirm Alzheimer's in a patient if they find one of the disease's main signs: the development, or buildup, of a sticky protein called beta-amyloid. Currently, doctors use brain imaging or a special test known as a spinal¹ tap to look for beta-amyloid buildup. Brain imaging is hard to get and spinal taps are painful.

Instead, many patients are diagnosed based on their behavior and cognitive² exams.

Now, labs have begun offering blood tests that can show some signs of Alzheimer's. Scientists are excited about the possibilities that the tests offer.

But the tests are not widely used yet because there is little data to guide doctors about which kind to order and when. The U.S. Food and Drug Administration (FDA) has not officially approved any of them, and few patients have insurance coverage³ for such tests.

"What tests can we trust?" asked Dr. Suzanne Schindler of Washington University in St. Louis. Schindler is part of a research project examining the tests. While some tests are very accurate, Schindler said, "other tests are not much better than a flip⁴ of a coin."

More than 6 million people in the United States and millions more around the world have Alzheimer's, the most common form of dementia. Its usual signs, or "biomarkers," are amyloid plaques⁶ and abnormal tau protein that leads to tangles⁷ that damage neurons.

New drugs such as Leqembi and Kisunla can slow the disease a little. The medicines remove amyloid from the brain. But these drugs only work in the early part, or stage, of Alzheimer's progression. Few patients get the costly⁸ brain scans and invasive spinal taps that could show early stage Alzheimer's.

Even specialists struggle to tell if Alzheimer's or something else is to blame for a patient's problems.

Schindler said she sometimes has patients "who I am convinced have Alzheimer's disease and I do testing and it's negative."

A limited number of doctors have carried out blood tests for Alzheimer's in carefully controlled research settings. However, a new study of about 1,200 patients in Sweden shows they also can work in doctors' offices.

The findings suggest the blood tests may be more helpful for general care doctors. They see many more cases of people with memory problems than specialists do. However, general care doctors have fewer diagnostic tools.

In the study, patients who visited either a general care doctor or a specialist for memory problems got an early diagnosis⁹ using traditional exams. They gave blood for testing and got confirmatory spinal taps or brain scans.

Blood testing is far more accurate, Lund University researchers reported recently at the Alzheimer's Association International Conference in Philadelphia. They said that the primary care doctors' first diagnosis was 61 percent accurate and the specialists' first diagnosis 73 percent. However, the blood test was 91 percent accurate, their study showed. The Journal of the American Medical Association published the study.

Different biomarkers

Dr. John Hsiao of the National Institute on Aging said the new tests measure different biomarkers in different ways.

Doctors and researchers should only use blood tests proven to have a greater than 90 percent accuracy rate, said Alzheimer's Association chief science officer Maria Carrillo.

Carrillo and Hsiao agreed that the blood tests most likely to provide that accuracy measure what is called p-tau217. Schindler helped lead an unusual direct comparison of several kinds of blood tests that came to the same finding. The Foundation for the National Institutes of Health financed the work.

That kind of test measures a form of tau that correlates with how much plaque⁵ buildup someone has, Schindler explained. A high level signals a strong likelihood the person has Alzheimer's. A low level strongly suggests Alzheimer's is not the cause of a patient's thinking problems.

Several companies are developing p-tau217 tests.

Who should use blood tests for Alzheimer's?

In the United States, only doctors can order the blood tests from labs. The Alzheimer's Association is working on policy suggestions and several companies plan to seek FDA approval, which would clarify correct use.

For now, Carrillo said doctors should use blood testing only in people with memory problems, after checking the accuracy of the kind they order.

Especially for primary care physicians, "it really has great potential to help them in sorting out who to give a reassuring¹⁰ message and who to send on to memory specialists," said Dr. Sebastian Palmqvist of Lund University. Palmqvist led the Swedish study with Lund's Dr. Oskar Hansson.

Words in This Story

diagnose - v. to identify a disease from its signs and symptoms

diagnosis - n. the act of identifying a disease from its signs and symptoms

accuracy - n. the quality of being precise or correct

cognitive - adj. of or relating to thinking, reasoning, or remembering

neuron - n. a cell that is the fundamental functional¹¹ unit of nervous tissue transmitting and receiving nerve impulses

correlate - v. to bear mutual relations

1 spinal   

adj.针的，尖刺的，尖刺状突起的；adj.脊骨的，脊髓的

参考例句：

• After three days in Japan,the spinal column becomes extraordinarily flexible.在日本三天，就已经使脊椎骨变得富有弹性了。
• Your spinal column is made up of 24 movable vertebrae.你的脊柱由24个活动的脊椎骨构成。

2 cognitive   

adj.认知的，认识的，有感知的

参考例句：

• As children grow older,their cognitive processes become sharper.孩子们越长越大，他们的认知过程变得更为敏锐。
• The cognitive psychologist is like the tinker who wants to know how a clock works.认知心理学者倒很像一个需要通晓钟表如何运转的钟表修理匠。

3 coverage   

n.报导，保险范围，保险额，范围，覆盖

参考例句：

• There's little coverage of foreign news in the newspaper.报纸上几乎没有国外新闻报道。
• This is an insurance policy with extensive coverage.这是一项承保范围广泛的保险。

4 flip   

vt.快速翻动；轻抛；轻拍；n.轻抛；adj.轻浮的

参考例句：

• I had a quick flip through the book and it looked very interesting.我很快翻阅了一下那本书，看来似乎很有趣。
• Let's flip a coin to see who pays the bill.咱们来抛硬币决定谁付钱。

5 plaque   

n.饰板，匾，(医)血小板

参考例句：

• There is a commemorative plaque to the artist in the village hall.村公所里有一块纪念该艺术家的牌匾。
• Some Latin words were engraved on the plaque. 牌匾上刻着些拉丁文。

6 plaques   

（纪念性的）匾牌( plaque的名词复数 )； 纪念匾； 牙斑； 空斑

参考例句：

• Primary plaques were detectable in 16 to 20 hours. 在16到20小时内可查出原发溶斑。
• The gondoliers wore green and white livery and silver plaques on their chests. 船夫们穿着白绿两色的制服，胸前别着银质徽章。

7 tangles   

（使）缠结， （使）乱作一团( tangle的第三人称单数 )

参考例句：

• Long hair tangles easily. 长头发容易打结。
• Tangles like this still interrupted their intercourse. 像这类纠缠不清的误会仍然妨碍着他们的交情。

8 costly   

adj.昂贵的，价值高的，豪华的

参考例句：

• It must be very costly to keep up a house like this.维修这么一幢房子一定很昂贵。
• This dictionary is very useful,only it is a bit costly.这本词典很有用，左不过贵了些。

9 diagnosis   

n.诊断，诊断结果，调查分析，判断

参考例句：

• His symptoms gave no obvious pointer to a possible diagnosis.他的症状无法作出明确的诊断。
• The engineer made a complete diagnosis of the bridge's collapse.工程师对桥的倒塌做一次彻底的调查分析。

10 reassuring   

a.使人消除恐惧和疑虑的，使人放心的

参考例句：

• He gave her a reassuring pat on the shoulder. 他轻拍了一下她的肩膀让她放心。
• With a reassuring pat on her arm, he left. 他鼓励地拍了拍她的手臂就离开了。

11 functional   

adj.为实用而设计的，具备功能的，起作用的

参考例句：

• The telephone was out of order,but is functional now.电话刚才坏了，但现在可以用了。
• The furniture is not fancy,just functional.这些家具不是摆着好看的，只是为了实用。