A blood test that gives a more accurate diagnosis of Alzheimer’s disease was announced at the July 2020 International Conference of the Alzheimer’s Association.
The Association estimates that approximately 5.7 million people in the U.S. are living with Alzheimer’s. That number is expected to triple by the year 2050.
The newly announced blood test, using blood samples from Alzheimer’s patients, analyzes brain protein in the blood. According to a recent article in Medical eXpress, the test registered a ninety percent accuracy in detecting indicators relating to Alzheimer’s. However, physicians treating Alzheimer’s patients would like to see even higher levels of accuracy which could take several more years.
Nonetheless, when finalized, the breakthrough will allow physicians to more easily identify patients who have the disease. The test is also designed to recognize people without symptoms but who will eventually succumb to Alzheimer’s.
How Did We Get Here?
Back in the 1990s, it was common to use brain MRI scans. However, technicians could not ascertain whether or not a patient’s cognitive loss was caused by Alzheimer’s. Top neurologists would occasionally misdiagnose the disease.
MRIs gradually became more accurate. Eventually, the MRIs could identify vascular disease. They could determine if someone had atrophy similar to Alzheimer’s or other dementia but the MRI could not definitively confirm the diagnosis.
The next step was to use diagnostic biomarkers to detect the disease. This is where MRI scans were on the scene showing shrinkage in areas of the brain associated with memory. They could not, however, confirm Alzheimer’s.
The New Diagnostic Landscape
Now with brain imaging, researchers can study these proteins as they accumulate along with disease progression.
Doctors would test suspected Alzheimer’s patients to determine whether tau, amyloid, or both are abnormal. One of the tests is a spinal tap to draw cerebro-spinal fluid. The doctors measure amyloid and tau levels which will have changed if there is a disease present.
A PET (positron emission tomography) scan is a second procedure that uses “tracers” that are in various stages of clinical development. The scans are safe but expensive costing upwards of $3,000. US Medicare does not cover the scans.
The medical community has been searching for a more convenient, less invasive, and less expensive way to diagnose Alzheimer’s. The researchers have found that answer in the new blood test.
The test, assessing the tau protein, has shown the highest degree of accuracy. Results were taken from testing three large patient populations.
Tau and Amyloid-β
For years testing has focused on tau for tangles and amyloid-β peptides for plaques. According to the National Institute of Health, tau accumulates in certain regions of the brain involving memory. Beta-amyloid forms plaques between neurons. These plaques and tangles disrupt the brain beyond repair.
Diagnosing People Over Eighty
It is even more difficult to determine whether changes in memory and thinking are age-related or signs of Alzheimer’s.
Unfortunately, until now the only 100 percent accurate diagnosis of Alzheimer’s occurred at autopsy. Two lesions were identified. The lesions are neurofibrillary tangles and beta-amyloid plaques. Occasionally during an autopsy, it was not uncommon to find that a person diagnosed with Alzheimer’s disorder also had a neurodegenerative disease associated with blood vessels in the brain.
Currently, there are various tests undergoing validation for accuracy, as they must function to near perfection. Each protein requires different methods in order to develop blood measurements.
The degree of success thus far has been about ninety to ninety-five percent in detecting the disease.
So far one test that measures Tau has met several criteria. The test found elevated tau in the brains of asymptomatic people. In these cases, people who are at risk have been identified and would be able to enter clinical trials hoping to prevent Alzheimer’s disease.
Lately, there has been considerable progress in finding cost-effective screening and tests, thus moving closer to treating the symptoms of Alzheimer’s or delaying its progression.