Listen to Australian and world news and follow trending topics with SBS News Podcasts.TRANSCRIPTDoctors say a new blood test may be able to predict the start of Alzheimer's symptoms years in advance.The test, which doctors say could be a game-changer, looks for what doctors call p-tau217 and can alert them to the disease five to ten years before healthy people develop symptoms.Dr Reisa Sperling from the Mass General Brigham Neuroscience Institute says the test was only being used on those with symptoms.“Right now it's really being utilized in people who already have symptoms of Alzheimer's disease and are thought to have cognitive impairment due to Alzheimer's disease In this study, we are looking at people who do not yet have symptoms of Alzheimer's disease."Currently, there is no effective drug which reverses the impacts of Alzheimer's.But findings from Dr Sperling's recent study, which saw participants ranging from 40 to 85 years old, could help scientists develop drugs that might prevent or delay Alzheimer's.“People who have very high levels of this blood test abnormality, p-tau217, were very likely to progress over time. So 38 per cent of them progressed to impairment within five years, and actually up to 78 per cent within 10 years