One of our earliest articles in 2016 for this series of “Wellness” was a discussion of how dedicated researchers had found two new substances to tag in patients with Alzheimer’s disease. This grave pathology can go almost undetected for many years and diagnosis usually comes late. The new focus of pharmacological research has changed to the earliest stages of the disease when amyloid starts to build up in the brain and drugs might make a difference; in order to achieve that a new laboratory test is needed.
A new report in Nature shows that a novel blood test that measures the amyloid biomarkers could be a reliable predictor of the presence of amyloid plaques in Alzheimer patients’ brains. Drs. Nakamura and Villemagne, from research centers in Japan and Australia respectively, described initial results on a blood test for amyloid-beta 9Abeta) that is similar to an earlier test developed by another team in Washington University of Saint Louis. At present researchers believe that the deposition of amyloid plaques can precede at least twenty years the first signs of cognitive decline, for which it is critically important to detect it early on to cure the patients.
The blood testing method consisted of isolating and concentrate three amyloid peptides (Abeta40, Abeta42 and APP699-71) from a sample that contained thousands of other proteins. They took advantage of data from two different cohorts of participants (some normal, some with mild cognitive decline and others with severe Alzheimer’s disease) that were studied previously in Japan (121 people) and Australia (252 people) where they compared the results of positron emission tomography (PET) with the testing of cerebrospinal fluid for amyloid. They calculated ratios of the different amyloid biomarkers and a composite score of multiple biomarkers; a rise in the composite index suggested that there was an active accumulation of amyloid in the brain.
The researchers claim that there was a 90% accuracy rate and a high correlation between the blood and cerebrospinal fluid tests. This test is more cost-effective than other types of testing, which could be the determinant factor in its approval by the public and private payors. It is still being developed and available only in the research labs.
There is a critical need for a safe and practical laboratory test to diagnose Alzheimer’s disease to screen the potential participants in clinical trial studies that usually span for several years. Participants that were initially deemed to have early signs of the disease—a diagnosis that is often very difficult for clinicians—ended up as not having it, which skewed the study results. Getting the right participants into the numerous studies underway is of humongous importance to find safe drugs to use early on.
Researchers are still tweaking the test to find out if it could be used to differentiate Alzheimer’s from other causes of cognitive decline like Lewy body dementia or Frontal lobe dementia; they also want to know if it can be used to track the progression or the disease or to assess the clinical response of patients to new drugs.
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