Blood Test for Beta Amyloid May Be Used to Predict Alzheimer Disease Risk

Researchers have developed a blood test for beta amyloid, a protein prevalent in Alzheimer disease. The test could be used in prevention trials to screen cognitively normal patients and determine which ones are at risk of developing the disease, according to a recent study published by the American Academy of Neurology.

The study included 158 volunteers in their 60s and 70s who were cognitively normal. The researchers from Washington University in St. Louis periodically conducted tests of memory and reasoning in addition to spinal taps and brain scans. Mass spectrometry was used to test the participants’ blood for beta amyloid and compared the beta amyloid levels to the results of the PET scans that the participants had received over the years.

The mass spectrometry identified that participants had accumulating beta amyloid in their brains even though their PET scans were negative; only years later did the scans reveal the protein in their brain. Furthermore, when combined with other factors that contribute to the risk of Alzheimer disease, the blood test was 94% accurate for predicting plaques, according to the research.

“Plasma Aβ42/Aβ40, especially when combined with age and APOE ε4 status, accurately diagnoses brain amyloidosis and can be used to screen cognitively normal individuals for brain amyloidosis,” explained the authors. APOE ε4 is a high-risk variant of the APOE gene, which is associated with Alzheimer disease.

“Individuals with a negative amyloid PET scan and positive plasma Aβ42/Aβ40 are at increased risk for converting to amyloid PET-positive. Plasma Aβ42/Aβ40 could be used in prevention trials to screen for individuals likely to be amyloid PET-positive and at risk for Alzheimer disease dementia.”

Despite the significant results, the researchers noted the potential limitations—amyloid is a normal brain protein and therefore may not be distinguishable for Alzheimer’s diagnoses.

“We don’t know if it has a function,” lead author Suzanne Schindler, MD, PhD, a neurologist at Barnes-Jewish Hospital in St. Louis, Missouri, told The New York Times. “It might just be a piece of trash.”

Although the test will not be available commercially for many years, the results may be important to consider for Alzheimer’s disease drug trials going forward, the researchers concluded.

Reference

Schindler S, Bollinger J, et al. High-precision plasma β-amyloid 42/40 predicts current and future

brain amyloidosis [published online August 1, 2019]. Am Acad Neurol. https://doi.org/10.1212/WNL.0000000000008081.