Neurologists diagnose cognitive impairment by examining memory and thinking skills. To find out if Alzheimer’s disease is causing the cognitive problems, they need evidence of specific brain changes.
These changes are usually found using brain scans or spinal taps. Knowing if a person’s cognitive issues are due to Alzheimer’s is crucial now because new treatments can change the course of the disease.
To make diagnosing Alzheimer’s easier for patients, several companies have started selling blood tests. These tests are meant to detect Alzheimer’s by analyzing the blood. At least five companies now offer these tests to doctors.
However, doctors have had no way of knowing which test is the most accurate because the tests had not been compared directly using the same group of people, methods, and criteria.
Dr. Suzanne Schindler and her team at Washington University School of Medicine in St. Louis compared the accuracy of six commercial blood tests. Four of these tests are available for doctors to use.
The team focused on how well these tests could detect signs of Alzheimer’s disease, especially the presence of amyloid plaques in the brain.
They found that some of the tests are accurate enough to replace spinal taps and brain scans for many patients. These findings are being presented at the Alzheimer’s Association International Conference in Philadelphia.
Dr. Schindler emphasized that some blood tests are accurate while others are not, leaving doctors unsure which ones to use. This head-to-head comparison gives doctors better information to help them choose the most accurate tests for diagnosing their patients.
Confirming that cognitive problems are due to Alzheimer’s early on is important. Early diagnosis ensures that patients can access the newest Alzheimer’s treatments.
In the past two years, the Food and Drug Administration (FDA) has approved two drugs that slow the disease’s progression. These drugs target amyloid, a protein that builds up in the brains of people with Alzheimer’s.
Doctors must confirm amyloid buildup in the brain before prescribing these treatments. Additionally, the diagnosis needs to be made early because the drugs are only approved for people with very mild to mild symptoms.
Dr. Schindler’s team evaluated how well six blood tests detected Alzheimer’s-related proteins in the blood. These proteins are linked to key features of Alzheimer’s: amyloid plaques, tau protein tangles in the brain, reduced brain volumes, and cognitive impairment.
The tests were developed by ALZpath, C2N Diagnostics, Fujirebio Diagnostics, Janssen, Quanterix, and Roche Diagnostics. C2N Diagnostics is a startup from Washington University, using technology licensed from the university.
The study used blood samples and data from the Alzheimer’s Disease Neuroimaging Initiative (ADNI), a long-term, multisite project aimed at identifying Alzheimer’s biomarkers.
The study included 392 people who provided blood samples within six months of having brain scans. The participants’ median age was 78.1 years, and about half had cognitive impairment.
Each test measured one or more biomarkers in the blood linked to Alzheimer’s. Across the six tests, five different biomarkers were measured. One biomarker, found in four tests, was especially good at identifying Alzheimer’s signs: phosphorylated tau 217 (p-tau217).
Some researchers thought multiple biomarkers would be needed to capture Alzheimer’s various features.
However, the study found that p-tau217 alone could accurately predict amyloid and tau levels in the brain, brain volumes, and cognitive symptoms. It outperformed other biomarkers and combinations of biomarkers.
The four tests measuring p-tau217 all performed well, regardless of the method used. The top performers were C2N Diagnostics’ PrecivityAD2 and Fujirebio’s Lumipulse.
Recently, the Global CEO Initiative on Alzheimer’s Disease published guidelines for using blood tests in clinical care.
They recommended that blood tests should be as accurate as FDA-approved cerebrospinal fluid tests, which are about 90% accurate at identifying Alzheimer’s in people with cognitive impairment. In this study, the p-tau217 tests met that standard, but the others did not.
This research provides hope for more accessible and accurate Alzheimer’s diagnosis through blood tests, potentially changing how the disease is diagnosed and treated in the future.
If you care about Alzheimer’s disease, please read studies that bad lifestyle habits can cause Alzheimer’s disease, and strawberries can be good defence against Alzheimer’s.
For more information about brain health, please see recent studies that oral cannabis extract may help reduce Alzheimer’s symptoms, and Vitamin E may help prevent Parkinson’s disease.
The research findings can be found in Nature Reviews Neurology.
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