Scientists have developed a new method to detect signs of Alzheimer’s disease in the blood, hopefully providing a cheap and reliable alternative for those who don’t have access to expensive brain scanning services.
Alzheimer’s disease is a progressive brain disorder that slowly destroys memory and thinking skills. According to the National Institution of Health, there are about 5.8 million people in the United States living with Alzheimer’s and related dementia.
Under current diagnostic criteria, a doctor must identify three hallmarks of Alzheimer’s disease in the patient’s brain before a diagnosis can be made: amyloid plaques, which are buildups of protein fragments that can disrupt the communication between brain cells; tau tangles, which occurs when a protein called tau become abnormally shaped and can no longer help transport nutrients and other essential substances in nerve cells; and evidence of neurodegeneration, which occurs when nerve cells deteriorate and die.
To identify these clinical features, patients usually have to either go under magnetic resonance imaging (MRI) or positron emission tomography (PET) scans, or have the doctor analyze samples of their cerebrospinal fluid, collected by inserting a needle into the spine.
These limitations, Karikari said, highlight the need of a less invasive, less resource-demanding approach that can detect signs of Alzheimer’s in the blood without compromising on reliability.
“A blood test is cheaper, safer and easier to administer, and it can improve clinical confidence in diagnosing Alzheimer’s and selecting participants for clinical trial and disease monitoring,”
A diagnostic blood test for Alzheimer’s disease is not a new idea. In fact, current blood tests can accurately detect amyloid plaques and tau tangles in a patient’s brain. However, there was a problem with detecting markers of neurodegeneration, the last of three key characteristics of Alzheimer’s.
Prior to the study, the best biomarker of neurodegeneration in blood plasma is called neurofilament light chain (NfL), a protein marker of nerve cell damage. The problem was that blood levels of NfL can be elevated in a wide range of neurodegenerative disorders, rendering it less useful when trying to determine whether the patient actually has Alzheimer’s rather than other brain conditions.
To solve the issue, Karikari and his team created an antibody that selectively binds to a biomarker of Alzheimer’s-specific neurodegeneration called “brain-derived tau,” or BD-tau, while avoiding tau proteins that aren’t produced by brain cells. They validated the BD-tau test in over 600 patient samples, including those from patients whose Alzheimer’s diagnosis was confirmed after their deaths, as well as from patients with memory deficiencies indicative of early-stage Alzheimer’s.
The team is planning to further study the effectiveness of BD-tau blood test with a large-scale clinical validation that involves a wide range of participants, including people of different racial and socioeconomic backgrounds, patients at different stages of the disease, and older adults who show no evidence of the disease at all.
“These projects are crucial to ensure that the biomarker results are generalizable to people from all backgrounds, and will pave the way to making BD-tau commercially available for widespread clinical and prognostic use,” the scientists said.
