Is There a Blood Test to Diagnose Alzheimer's Disease?

To make a diagnosis of Alzheimer's disease most physicians will look for:

• the presence of amyloid plaques in the brain
• the presence of tau tangles in the brain
• neurodegeneration or shrinking of the brain

They typically do this by looking at imaging tests or analyzing cerebrospinal fluid (by performing a spinal tap, which can be painful).

In the recent few years, researchers have been experimenting with developing blood sample tests that can detect different biomarkers and compounds associated with the disease. So, current blood diagnostic methods can detect abnormalities in plasma amyloid beta and a phosphorylated form of tau, but there is no great way, as of yet, to detect markers of brain neurodegeneration.

Therefore, blood tests results alone cannot be and should not be used to make an official Alzheimer's diagnosis.

However, earlier in 2023, it was announced that there was some promising results in researchers testing the ability to detect Alzheimer's biomarkers through a simple finger prick test. The test was more than 80% accurate in identifying Alzheimer's-related changes. The blood test was found to be more accurate than a PCP's diagnosis and the PCP's who they compared the diagnostic accuracy of the test to admitted that they were less than 50% certain about the diagnosis that they determined after attempting to identify on their own the presence of Alzheimer's-related changes.

‍

However, as of yet, there are only a few blood tests on the market that can be ordered by a healthcare provider to aid in Alzheimer's disease diagnosis and none of them have FDA approval at this time.

So, yes, technically there are blood tests that can HELP diagnose Alzheimer's disease by detecting certain biomarkers or compounds associated with the disease. But, a blood test should not be used as the only diagnostic tool just yet, and physicians should be using a combination of diagnostic tools, medical history gathering, neurological exams, cognitive assessments, brain imaging, and blood tests to make an accurate diagnosis.

If you or someone you know is concerned about dementia-like symptoms including changes in mood and behavior please follow-up with the primary care physician first. The primary care physician can then refer you to a specialist such as a gerontologist, neurologist, and/or neuropsychologist based on their findings.

‍

References: 

https://www.upmc.com/media/news/122722-alzheimers-neurodegeneration

https://www.nia.nih.gov/health/how-alzheimers-disease-diagnosed

https://aaic.alz.org/releases_2023/finger-prick-blood-test-alzheimers-disease.asp

https://www.alz.org/alzheimers-dementia/diagnosis/medical_tests