Biomarker Tests for Alzheimer’s and Dementia

Researchers from McGill University in Montreal have published an interesting study on testing DHEA levels in blood samples as a method to screen for Alzheimer’s and other forms of dementia. DHEA is a naturally occurring steroid that is present in the brain.

The results of the study indicate that blood drawn from Alzheimer’s patients had lower levels of DHEA compared to healthy controls (specifically, DHEA levels after oxidation were significantly lower in the Alzheimer’s subjects).

So, what does this mean on a practical level for Alzheimer’s and dementia screening? Blood tests can hold the future promise of a dementia screening tool in the doctor’s office, at least in theory. However, there are some challenges to overcome before this could become a reality, including:

1. Reliability – many biomarker tests have been shown to have very high false-positive rates (the test shows you have the disease when you really don’t) or alternately false-negative (you *do* have the disease, but the test misses it).

2. Sensitivity – do biomarker tests distinguish between mild cognitive impairment (MCI), Alzheimer’s, and other forms of dementia? A few of the newer computerized cognitive testing tools do a decent job at differentiating between different levels of cognitive impairment, but it isn’t clear if a blood test would work for this purpose.

It could turn out that a DHEA blood test for dementia may only confirm that a patient does have the disease, rather than provide an early warning system. More work needs to be done in this area.