Alzheimer's disease (AD) is a progressive, neurodegenerative disease, for which there is no cure. Hundreds of research studies are ongoing, and those studies are essential to finding a cause, possible treatments and a way to detect the disease before it has progressed too far. Estimates from the WHO and the CDC show that nearly 15 million Americans suffer from the disorder and worldwide that number jumps to more than 44 million. The numbers are going nowhere but up, and it's become a global health concern.
Scientists in Japan and Australia have developed a blood test that they believe can detect levels of a protein that is associated with AD. Tau protein in the brain is what causes cognitive decline and loss of motor function in patients with AD. It can sometimes be detected in blood tests, but these proteins get broken down in the bloodstream and do not reliably show up in the currently available biomarker assays. Beta-amyloid deposits can be seen on PET scans of the brain, but by the time they are visible on imaging scans, the disease has progressed too far for much to be done.
If the test is found to be accurate in further research, the benefit could be that clinical trials will be designed better and yield more useful results. Since there is no precise way to tell what stage of AD a patient might be in, finding subjects for drug trials can be hit or miss. PET scans are not reliable enough and measuring levels of protein in cerebral spinal fluid is uncomfortable for the study participants and expensive. To date, every drug for Alzheimer's has failed in clinical trials. Part of the reason could be that the participants might have advanced disease and many of the drugs are meant to help those in the early stages since slowing the progression of AD has been the goal of many trials.
Molecular biologist Katsuhiko Yanagisawa at the Center for Development of Advanced Medicine for Dementia in Obu, Japan, and his colleagues developed the most recent prototype biomarker test. Their work is published online in the journal Nature 1. Brisbane-based scientist James Doecke, who was also involved in the research, said that it had been a "very difficult journey" in refining the test. Blood samples were collected every 18 months to two years from 121 patients in Japan and 252 patients in Australia. The study patients underwent PET scans and tests of cerebral spinal fluid as well, and the results of the blood tests were compared to those tests to assess accuracy. Dr. Doecke explained, "A lot of labs around the world have designed an assay and tried to find the protein in the blood that we can test easily that will be correlated with the disease, and nobody's come up until now with something this strong. Previously we've only been 80 percent accurate, and now we're greater than 90 [per cent] — what it means is that we can better direct our clinical trials to the right population."
Colin Masters, a professor at the Florey Institute of Neuroscience and Mental Health has studied AD for three decades. He told ABC news in Australia, "The performance of the blood test is so good, it has accuracy of approximately 90 percent." Measuring the small fragments of amyloid-β fragments in blood samples, including another protein that is a precursor to amyloid-β involved combining two existing methods, immunoprecipitation and mass spectroscopy. These techniques are being fine-tuned by the researchers who hope to conduct more extensive trials to validate these early results. The video below features Professor Masters explaining more about the research, check it out.
Sources: Nature, ABC Australia, Journal article, Nature