New Alzheimer’s blood test predicts who is likely to develop dementia in 5 to 10 years By Latest & Breaking News on Fox News Comments Off on New Alzheimer’s blood test predicts who is likely to develop dementia in 5 to 10 years 2 Min Read A p-tau217 blood test predicted a 78% chance of cognitive decline within 10 years for symptom-free adults with very high levels of the biomarker.