New blood tests for Alzheimer’s disease offer a potential way to diagnose it sooner and get patients on the road to treatment.
Several blood tests are now available, but experts have yet to assess how accurate they are compared to more complex or invasive brain scans and cerebrospinal fluid tests, which are currently considered the diagnostic standard.
But a new study, conducted by experts from the Washington University School of Medicine in the US, aims to change that.
Scientists compared six blood tests for Alzheimer’s. These tests measure different molecules in the blood, called biomarkers, that indicate that someone has the disease. They wanted to see if these tests were as accurate as current methods.
To do this, they compared blood samples from 392 patients, of which an average of 78 patients showed cognitive impairment, a possible sign of the disease.
While a range of blood tests are now available, experts have yet to assess how accurate they are compared to more complex or invasive brain scans and spinal fluid tests, which are currently considered the diagnostic standard.
The experts presented their findings today at the Alzheimer’s Association International Conference in Philadelphia, saying that of the six tests, four reached a 90 percent accuracy threshold.
They noted that all four tests were designed to target one specific biomarker, a form of tau known as phosphorylated tau 217 (p-tau217).
Tau is a type of protein found in the brain that functions abnormally in Alzheimer’s patients. It forms tangles that impede the functioning of neurons, leading to a variety of problems, the most well-known of which is dementia.
According to Suzanne Schindler, the project’s principal investigator and an expert in neurology, such direct comparisons are important so doctors can treat their patients more effectively.
“Some blood tests are accurate, some are not, and doctors don’t know which tests to use,” she said.
‘Thanks to this direct comparison, doctors now have more reliable information about which tests can best help them accurately diagnose their patients.’
The six tests analyzed were performed by the companies ALZpath, C2N Diagnostics, Fujirebio Diagnostics, Janssen, Quanterix and Roche Diagnostics.
Of these, ALZpath, C2N Diagnostics, Fujirebio Diagnostics, and Janssen, which investigated P-tau 217, performed best according to the authors. Of this subgroup, C2N Diagnostics performed best, Fujirebio Diagnostics.
Ms Schindler said the diagnostic accuracy of the tests should be equal to that of cerebrospinal fluid tests, which are approved in the US for diagnosing Alzheimer’s.
“We concluded that to be used without a second test, blood tests would have to be as accurate as the FDA-approved cerebrospinal fluid tests, which are about 90 percent sensitive and specific in identifying Alzheimer’s disease in people with cognitive impairment,” she said.
‘In the current study, the p-tau217 tests met that standard, but the others did not.’
According to fellow researcher Kellen Petersen, also an expert in neurology, the identification of a single biomarker as a differentiator in the head-to-head comparison of the tests, compared with a combination of biomarkers, was contrary to some expectations.
It is currently thought that around 900,000 Britons suffer from the memory-robbing disorder. But scientists from University College London estimate that this number will rise to 1.7 million within two decades as people live longer. It is a 40 per cent increase on the previous forecast in 2017.
“Some people thought we needed to measure multiple biomarkers to map out the different features of Alzheimer’s disease. That’s not what we found,” he said.
‘P-tau217 alone can do it all. It accurately predicted brain amyloid and tau levels, brain volumes, and cognitive symptoms. It was more accurate than any other biomarker, or indeed any combination of biomarkers, across the board.’
The authors stress the importance of rapid and accurate testing for Alzheimer’s, as the U.S. Food and Drug Administration recently approved two drugs that slow the progression of the disease.
Although the drugs, such as lecanemab and donanemab, are considered groundbreaking, they only work effectively when Alzheimer’s is in the early stages. Rapid diagnosis is therefore essential for their success.
With the UK currently facing a shortage of Alzheimer’s testing capacity, experts warn that as many as four in five patients who could benefit from the new drugs could be left out.
Lecanemab and donanemab are not currently approved in the UK, but UK regulators are expected to make a decision this year.
The study has a number of limitations. First, it is presented at a conference and has not been published in a peer-review journal.
Another limitation mentioned by the authors themselves is the small sample size used in the study.
Commenting on the research, Dr Jacqui Hanley, head of research funding at the charity Alzheimer’s Research UK, said: ‘Too many people in the UK are waiting anxiously for a dementia diagnosis. On average, they wait up to two years, and more than four years if they are under 65.’
‘Blood tests, in combination with other tests, show promise in diagnosing the diseases that cause dementia. They can be faster, but just as accurate, as PET scans and lumbar punctures.
‘But neither method has been validated for use as part of the diagnostic pathway in the UK.’
She said the recent research was promising, despite some limitations.
“This study, conducted in the US and still undergoing peer review, compares several commercial blood tests and current diagnostic methods to determine which method is most accurate in diagnosing Alzheimer’s disease,” she said.
There are several possible signs of dementia, a memory-destroying condition that affects nearly 1 million Britons and seven million Americans
‘It adds to the growing evidence that blood tests, particularly those that measure levels of p-tau217, can diagnose Alzheimer’s and other causes of dementia. What’s more, they have the potential to revolutionize the way dementia is diagnosed.
“However, the companies that provided the tests for this study also provided the data, which was limited. And only a small number of people were included, so they were not representative of the general population.”
Dr Hanley added that such blood tests would need to be tested on a larger scale before being introduced in the UK. Alzheimer’s Research UK was already funding projects to make this happen.
“This ground-breaking project aims to change the way dementia is diagnosed by validating blood tests for dementia that could be used across the NHS within the next five years,” she said.
In the UK, Alzheimer’s is usually diagnosed after a mental test to determine whether a patient shows signs of cognitive impairment.
This will be followed by some further tests, such as a brain scan, to determine whether Alzheimer’s is the most likely cause.
The NHS warns that it may take several appointments and tests, spread over many months, before an Alzheimer’s diagnosis is confirmed.
Hundreds of participants were assessed on how healthy their lives were, scoring them between zero and six based on all the different factors. Volunteers who didn’t sweat for at least ten minutes a day for three or four days a week got nothing. The other lifestyle habits were alcohol consumption, smoking status, and sleep quality. Social interaction and having hobbies were the other two factors
Although Alzheimer’s is the leading cause of dementia, other health problems, such as reduced blood flow to the brain (vascular dementia), must also be considered.
Charity The Alzheimer’s Society reports that there are currently around one million people living with dementia in the UK, with this number expected to rise to 1.4 million by 2040.
An estimated 7 million people in the US are now living with dementia.
This comes as promising research suggests a diabetes vaccine, already prescribed to thousands of NHS patients, could reduce the risk of developing Alzheimer’s.
Liraglutide, sold under the brand name Saxenda, is marketed to people with type 2 diabetes because it lowers blood sugar levels and promotes weight loss.
Research now suggests that once-daily injections can slow cognitive decline in Alzheimer’s patients by as much as 18 percent.
Researchers said today that the findings “offer hope” and could pave the way for new treatments for dementia, meaning further research is vital.