Blood Tests for Alzheimer's

Contributed by: Dennis Fortier, President, Medical Care Corporation

Bio-marker development is a very common news topic in the Alzheimer's field. Each day there is news about a blood test, a spinal assay, a binding agent that aids imaging, or a new cognitive measure. These developments are important as they will lead the way to earlier detection and more accurate diagnoses -- two areas where improvements could have a great positive impact on treatment outcomes.

A particular approach that has gotten a lot of media attention, including this story today, is to measure the amount of beta-amyloid in the blood. The theory is that people with subtle memory loss and high levels of beta-amyloid may be in the early stages of Alzheimer's disease and should be treated immediately before symptoms worsen. Those with subtle memory loss and normal levels of beta-amyloid probably have some other medical condition disturbing their memory.

While this work is theoretically intriguing, one particular obstacle still stands in the way of clinical utility. The challenge is that the beta-amyloid levels in the blood of healthy individuals range widely. Therefore, it is difficult to meaningfully identify the "normal" level in any given patient. As such, measuring amyloid in the blood or spinal fluid is a promising avenue but still quite some time from clinical feasibility.

One possible improvement in this approach is to compare the ratio of beta-amyloid to tau proteins in the blood. Doing so may offer a more meaningful measure, particularly when observed over time within a given patient. A rapidly changing ratio may indicate pathological changes that foretell the onset of Alzheimer's disease. Work on this approach is proceeding at several locations.

We look forward to ongoing news and developments in this area. For the time being, the most accurate and clinically feasible bio-marker is cognition. Eventually, it is likely that a combination of biomarkers will be used in conjunction to accurately identify diseases and medical conditions in early stages when treatment effect is optimal.

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