Can blood tests help diagnose Alzheimer dementia?

Huge changes are coming to how we diagnose and treat Alzheimer dementia. The 2 minute update looks at a study evaluating blood biomarkers to help us improve accuracy of that diagnosis.

 

1213 patients with cognitive symptoms were included in this study. Mean age was 74, and it was almost exactly half men and half women.

In the initial group, about half of the patients had blood drawn to determine cutoff values for 4 tau and amyloid proteins. The remaining patients were in a prospective cohort. They all received cognitive testing, imaging and blood testing.

 

There are tons of statistics in the study, but it found that overall accuracy improved dramatically when blood biomarkers were added. If a patient saw a primary care provider, the diagnosis was accurate only 61% of the time. Dementia specialists fared better, but accuracy was still quite low at 73%. Adding the blood test improved accuracy to 91%.

 

This is not ready for use, but appears promising. We already have similar CSF testing, but blood draws are much easier. The hope is that we can determine who is high risk for developing Alzheimer dementia, and use new treatments to remove amyloid from the brain before dementia develops. But those new treatments have not been shown to prevent dementia, only to slow cognitive decline in people who already have symptoms.

 

All of these patients had cognitive symptoms. Accuracy will very likely fall if we are screening people who do not have symptoms. So there’s a lot of work to do before we really know how to use these kinds of tests. But the Alzheimer’s Association has already said that “…detection of AD neuropathologic change by biomarkers is equivalent to diagnosing the disease ... symptoms are a result of the disease process and are not necessary to diagnose the disease.”

 

References: Palmqvist et al. Blood Biomarkers to Detect Alzheimer Disease in Primary Care and Secondary Care. JAMA 2024 July 28:e2413855 and Jack et al. Revised criteria for diagnosis and staging of Alzheimer’s disease: Alzheimer’s Association Workgroup. Alzheimer's & Dementia 2024;20:5143