Alzheimer's blood tests may predict symptoms years in advance, but experts urge caution

A new blood test may predict Alzheimer's symptoms years in advance, offering hope for earlier detection, but experts urge caution due to concerns about accuracy and reliability. The test measures levels of p-tau217, a protein that accumulates in the brain during Alzheimer's disease. Repeated blood tests predicted the age of symptom onset with a median absolute error of about three to four years.