Alzheimer's blood test could identify risk up to 10 years before symptoms start

• A blood test measuring the Alzheimer’s biomarker p-tau217 suggests cognitively healthy older adults with very high levels had an estimated 38% risk of developing cognitive impairment within 5 years, rising to up to 78% over 10 years.
• Elevated p-tau217 levels were associated with future cognitive impairment independently of existing risk measures, such as amyloid PET scan findings and genetic risk factors, including the APOE4 variant.
• The predictive blood test could help identify people at higher risk for cognitive decline who may be suitable candidates for clinical trials of emerging preventive therapies.
• However, as there are currently no proven disease-modifying treatments for asymptomatic people at high risk, the test is not currently recommended for routine screening of healthy adults.

Blood-based biomarkers offer a less invasive and more accessible alternative to brain scans or spinal fluid tests for detecting biological changes associated with Alzheimer’s disease.

One of the most promising markers is phosphorylated tau 217 (p-tau217), a protein linked to the disease process long before memory problems become apparent.

A blood test measuring p-tau217 has Food and Drug Administration (FDA) approval for certain clinical uses. However, questions remain about how well it can predict whether someone without symptoms will eventually experience cognitive decline.

Now, a new study suggests p-tau217 blood tests may be able to predict the risk of developing symptoms of Alzheimer’s in cognitively unimpaired adults up to a decade early.

The study, presented at the Alzheimer’s Association International Conference and published simultaneously in JAMA, found that older adults with very high blood levels of p-tau217 were substantially more likely to develop cognitive impairment over the following decade than those with lower levels.

However, the study authors add that the test is not yet ready for routine screening of healthy adults, but the findings could play an important role in future prevention trials and personalized risk assessment.