Study: Alzheimer's blood test diagnosed 91% of dementia cases

A new study shows a blood test for Alzheimer's worked better than the cognitive tests and brain scans doctors use for diagnosis now.

Researchers from St. Louis and Sweden tested a group of about 1,200 patients — all of whom took a blood test called PrecivityAD2.

Half were seen by a primary care doctor, the other half by a dementia specialist.

They also were diagnosed using spinal taps and brain scans.

The new test uses a proprietary algorithm that looks at amyloid and tau protein ratios — hallmarks of the memory robbing disease.

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The blood test was 91% accurate, compared to the usual rates of 61% accurate in primary care cases where the patient is diagnosed by their primary doctor and 73% accurate for those diagnosed by a dementia specialist.

Alzheimer's advocates have been pushing for more blood based tests to help doctors diagnose patients, especially those with early signs of the illness, like mild cognitive impairment.

The study faced potential limitations: All of the tests were run by one lab, the study lacked a diversity in patients and the test is not FDA approved — nor is it covered by Medicare.

More research needs to be done to see if the results could be replicated by other studies.

There are currently more than a dozen blood test for Alzheimer's in development — none are yet FDA approved.