’Blood tests to measure amyloid protein, and possibly tau protein, are becoming much more sensitive and reliable enough to become routine aids in helping to diagnose AD.
These various tests are at different stages of validation – assuring they’re accurate across many different populations. And, for each protein, there are several different methods for making the blood measurements. So there is still work to do before any of these tests will be widely used in medical practice. Predictions are difficult, but without any more difficulties, we hope they can be applied in a few years.
To be useful, these tests have to be nearly perfect predictors. They aren’t there yet; so far, they seem to get it right about 85–90+% of the time. This accuracy will be even more important if they’re to be used to identify people for new therapies.
It’s still too early to tell if one AD blood test will prove better than the others. However, given the long road to this point, the research community is excited about the possibilities.
The tests measuring amyloid actually measure the ratio of two different sizes of the amyloid peptide – similar to using the ratio of HDL to LDL blood cholesterol to evaluate lipids. If the ratio of the amyloid is decreasing in blood, it is accumulating in the brain, even before AD symptoms emerge. Their first use, however, will be in diagnosis of people with symptoms.
What the blood assays for the tau protein, the main component of tangles in the brain, tell us is little less certain. Most in the field believe, however, that they will may provide information on the stage or progression of the disease.
Collectively, these tests mark real progress. More certain, earlier and cost-effective diagnostic aids will help all of us reach our goal of finding novel treatments that can better treat the clinical symptoms of AD and/or delay its development.…’
Via The Conversation