A recent study has shown that a combined blood test has a 90% accuracy rate in diagnosing Alzheimer’s disease, significantly higher than the accuracy rates of neurologists (73%) and primary care doctors (61%). This test measures plasma phosphorylated tau 217 (p-tau217) and the amyloid 42/40 ratio, key biomarkers for Alzheimer’s. The combination of these measures, known as the amyloid probability score, provides a highly predictive assessment.
The p-tau217 biomarker, which indicates amyloid pathology, has profound implications for diagnosing Alzheimer’s, as its levels are notably higher in affected individuals. Previous research has demonstrated that p-tau217 tests can identify elevated levels of beta-amyloid with up to 96% accuracy and tau with up to 97% accuracy. These findings suggest that the presence of beta-amyloid and tau tangles are definitive markers of Alzheimer’s disease.
The study’s blood test was validated against spinal fluid taps, which, along with amyloid PET scans, are the current gold standards for Alzheimer’s diagnosis. These traditional methods are costly and invasive, making the blood test a potentially revolutionary tool in Alzheimer’s diagnosis. However, current cognitive assessments and brief tests used by doctors often misdiagnose Alzheimer’s due to the similarity of its symptoms to other conditions such as vascular dementia, depression, and vitamin B12 deficiency.
While the blood test holds promise for quicker and more accurate diagnoses, routine use in primary care is still on the horizon. More research, physician education, and guideline development are necessary. Nevertheless, the potential for such blood tests to reduce diagnostic wait times and improve early intervention is significant. In the meantime, lifestyle changes like regular exercise, a Mediterranean diet, and managing vascular risk factors can help prevent or slow cognitive decline.
For more information see Pam Belluck “A Blood Test Accurately Diagnosed Alzheimer’s 90% of the Time, Study Finds” The New York Times, July 28, 2024.
Special thanks to Lewis Saret (Attorney, Washington, D.C.) for bringing this article to my attention.
https://lawprofessors.typepad.com/trusts_estates_prof/2024/07/a-blood-test-accurately-diagnosed-alzheimers-90-of-the-time-study-finds.html