Today, the only way to definitively diagnose Alzheimer’s disease in life is through brain scans and tests of cerebrospinal fluid that must be collected via lumbar puncture.
Though cumbersome and expensive, such tests provide the most accurate diagnoses for patients. Investigators at Brigham and Women’s Hospital are working to develop a blood test that could replace these procedures to accurately diagnose or even predict Alzheimer’s disease before symptoms appear.
The tau protein has long been implicated in Alzheimer’s , however, tau occurs as a family of related molecules which have subtly different properties.
The Brigham team took advantage of the complexity of tau and built assays to measure different forms of tau and identified a subset of tau proteins which are specifically elevated in Alzheimer’s disease.
In the study paper, the researchers explain that the test may be able to detect biomarkers of Alzheimer’s disease before the appearance of obvious symptoms.
Tau proteins are made of related molecules with somewhat different properties.
In the new study, the researchers started by devising a method to identify the specific subset of tau molecules that appear at high levels in Alzheimer’s disease.
The researchers came up with ways of detecting different types of tau molecules in both blood and cerebrospinal fluid, and they tested these methods in samples of plasma (a blood component) and cerebrospinal fluid from two sets of participants (65 in the first group and 86 in the other).
One group of samples came from volunteers enrolled in the Harvard Aging Brain Study, and some who had participated in research at the Institute of Neurology in London, United Kingdom.
The second group came from volunteers recruited by specialists at the Shiley-Marcos Alzheimer’s Disease Research Center at the University of California, San Diego.
The team assessed five tests for tau molecules, looking to see which would be most effective. In the end, the scientists settled on a test that they called “the NT1 assay,” which demonstrated both sensitivity and specificity, meaning that it was able to accurately detect Alzheimer’s.
“A blood test for Alzheimer’s disease, could be administered easily and repeatedly, with patients going to their primary care office rather than having to go into [the] hospital,” claims study author Dominic Walsh.
“Ultimately, a blood-based test could replace cerebrospinal fluid testing and/or brain imaging,” he suggests, adding, “Our new test has the potential to do just that.”
“Our test will need further validation in many more people, but if it performs as in the initial two cohorts, it would be a transformative breakthrough,” explained Walsh
The researchers stress that while they verified the test in blood samples from two different cohorts, they will need to conduct further trials with larger groups of participants to fully establish the effectiveness of the test.
Also, they now aim to learn more about how tau protein levels change as the condition progresses, compared with their levels before Alzheimer’s symptoms set in.
“We’ve made our data and the tools needed to perform our test widely available because we want other research groups to put this to test. It’s important for others to validate our findings so that we can be certain this test will work across different populations,” notes Walsh.
Source: Medical News Today