Blood tests to detect Alzheimer’s disease may be just around the corner

WASHINGTON-

New blood tests could help doctors diagnose Alzheimer’s disease more quickly and accurately, researchers said Sunday, although some appear to work faster than others.

It’s difficult to determine whether memory problems are caused by Alzheimer’s disease. It requires confirming one of the disease’s hallmarks — a buildup of a sticky protein called beta-amyloid — with hard-to-reach brain scans or an awkward spinal tap. Instead, many patients are diagnosed based on symptoms and cognitive tests.

Labs have begun offering a series of tests that can detect some signs of Alzheimer’s in the blood. Scientists are excited about their potential, though the tests have not yet been widely used because there is little data to help doctors decide which ones to prescribe and when. The U.S. Food and Drug Administration has not formally approved them, and health insurance coverage is limited.

“What evidence can we trust?” asked Dr. Suzanne Schindler, a neurologist at Washington University in St. Louis who has been involved in a research project exploring the issue. While some are highly accurate, “others are not much better than a coin flip.”

Demand for early diagnosis of Alzheimer’s disease is growing

More than 6 million people in the United States and many more around the world suffer from Alzheimer’s disease, the most common form of dementia. Its characteristic “biomarkers” are amyloid plaques that clog the brain and abnormal levels of the tau protein, which causes tangles that kill neurons.

The new drugs Lekembi and Kisunla can also moderately slow the deterioration of symptoms by removing amyloid deposits from the brain. But they only work in the early stages of the disease, and over time it can be difficult to provide patients with quality of life. Measuring the presence of amyloid in the cerebrospinal fluid is an invasive test. A special PET scanner to detect plaques is expensive, and it can take months to get an appointment.

Even specialists may have trouble determining whether a patient’s symptoms are caused by Alzheimer’s disease or something else.

“Quite often I have patients who I believe have Alzheimer’s disease, and I test them and they’re negative,” Schindler said.

New study suggests blood tests for Alzheimer’s could be quicker and easier

Until now, blood tests have been used mostly in tightly controlled research settings. But a study of about 1,200 patients in Sweden shows that they can also work in the madness of real-life doctors’ offices, especially primary care doctors’ offices, which see far more people with memory problems than specialists but have fewer tools to help them assess them.

In the study, patients who visited a primary care physician or memory specialist received an initial diagnosis using traditional tests, had blood drawn for testing, and were referred for a confirmatory lumbar puncture or brain scan.

Blood tests were much more accurate, Lund University researchers said Sunday at the International Alzheimer’s Association conference in Philadelphia. According to the results, which were also published in the Journal of the American Medical Association, the initial diagnosis by primary care physicians was 61 percent accurate, and the diagnosis by specialists was 73 percent accurate, compared with 91 percent for blood tests.

Which Alzheimer’s test works best?

There are a wide variety of offerings, says Dr. John Xiao of the National Institute on Aging. Each test measures different biomarkers in different ways.

Doctors and researchers should use only tests that are more than 90% accurate, said Maria Carrillo, scientific director of the Alzheimer’s Association.

Carrillo and Xiao agreed that current tests are likely to hit that figure by measuring something called p-tau217. Schindler helped lead an unusually direct comparison of several blood tests funded by the National Institutes of Health Foundation that came to the same conclusion.

This type of test measures the form of tau associated with plaque buildup in a person, Schindler said. A high level indicates a high likelihood that a person has Alzheimer’s disease, while a low level indicates that it is probably not the cause of memory loss.

Several companies are developing p-tau217 tests, including ALZpath Inc., Roche, Eli Lilly and C2N Diagnostics, which provided the version used in the Swedish study.

Who should have blood tests for Alzheimer’s disease?

Only doctors can order them from labs. The Alzheimer’s Association is working on protocols, and several companies are seeking FDA approval that would clarify their proper use.

For now, Carrillo said, doctors should only use blood tests on people with memory problems after checking the reliability of the type of test they order.

For general practitioners especially, “this has a really big potential to help them figure out who to give a reassuring message to and who to refer to memory specialists,” said Dr. Sebastian Palmqvist of Lund University, who led the study in Sweden along with Lund’s Dr. Oskar Hansson.

The tests are not yet indicated for people who have no symptoms but are concerned about Alzheimer’s in their family, unless it is part of a research study, Schindler stressed.

This is partly because amyloid buildup can begin two decades before the first signs of memory problems appear, and there are currently no preventative measures beyond basic recommendations for a healthy diet, exercise, and adequate sleep. However, research is underway into possible treatments for people at high risk of Alzheimer’s, and some of these involve blood tests.