Blood Test and Genetic Test: New Method Developed to Estimate When Alzheimer’s Symptoms May Appear

Researchers at Columbia University have developed a method to predict when people at high risk of Alzheimer’s disease may develop their first symptoms.

The method combines a blood test for the biomarker p-tau217 with a genetic test for the APOE4 gene variant, the strongest genetic risk factor for Alzheimer’s disease.

The study, whose findings were published in The Lancet Neurology, included approximately 8,500 participants from diverse ethnic backgrounds. The researchers studied people who had no symptoms of the disease at the time of assessment.

The researchers found that after p-tau217 levels increased, the estimated time to symptom onset varied substantially depending on the person’s APOE variant. For people with one or two copies of APOE4, the first symptoms could, according to the estimates, appear in approximately three to four years. For people with other APOE variants, the period was about five to six years.

p-tau217 is a biomarker associated with the accumulation of abnormal forms of amyloid and tau proteins in the brain. Tests for p-tau217 are already used to diagnose Alzheimer’s disease in older adults with memory and cognitive impairments. However, p-tau217 levels alone are not sufficient to reliably predict exactly when the disease will begin in an asymptomatic person.

According to study leader Richard Mayeux, combining the two tests significantly improves the accuracy of the prediction. The results were also comparable among people from different ethnic backgrounds.

About one in five people carries at least one copy of APOE4. However, the researchers emphasize that having this gene variant does not mean that a person will necessarily develop Alzheimer’s disease.

The authors believe the findings could become particularly important as preventive treatments emerge. Currently approved monoclonal antibodies for Alzheimer’s disease are intended for people who already have symptoms and are not used in asymptomatic patients.

This situation could change if ongoing studies show that antibody-based treatments can slow disease progression when given to people who have no symptoms but have elevated p-tau217 levels.

The new findings could also be used in the development and conduct of clinical trials of other drugs aimed at preventing Alzheimer’s disease.

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