After years of trying, we may finally have a simple blood test to diagnose Alzheimer's. Right now the only ways to tell are with extensive brain imaging, a spinal tap, or an autopsy of the brain after the person dies. That's why this new blood test is so exciting.

It detects various forms of the amyloid beta protein also called AB protein and their amounts in the blood. This may give doctors a measure of the accumulation of these proteins in the brain which would tell us the progression of the disease.

In Alzheimer's disease, the build-up the AB proteins in the cerebral cortex is called plaque. We actually don't know if the plaque causes Alzheimer's or just happens to be present along with the disease. We also have not established whether these AB proteins in the blood of patients contribute to the disease. Yet, this raises a startling question about whether Alzheimer's is transmissible by blood. A new study suggests this may be possible.

In an experiment researchers connected two mice sharing one circulating blood system. One mouse had been made to produce AB plaques and was already suffering symptoms of neurological damage. The other mouse was healthy and free of the AB protein and the goal was to see if it would develop plaques in its brain. Eventually it began showing signs of Alzheimer's.

This suggests the AB protein can be 'infectious' which would have huge implications about blood transfusions and tissue transplants. Only more research will clear up this question.

The good news is that one day, when we go in for our yearly physical, a simple blood test will give us a summary of our health including whether our poor memory is due to Alzheimer's and if so, to get treatment early.