Blood Test for Alzheimer’s

Earlier this week, a paper was published showing how, for the first time, a blood test may be used to predict whether a person will develop Alzheimer’s in the near future. Specifically, the blood test was able to predict with accuracy greater than 90% whether a person (70-years-old or older) would develop amnesic mild cognitive impairment (aMCI, the earliest detectable stage of Alzheimer’s) or mild Alzheimer’s disease (AD) within the next 2-3 years.

In the study, 74 participants had aMCI or AD – 46 of these people had the condition at the start of the study, while 28 converted over the course of the study. (53 additional participants were used as controls – they were similar in age, education, and gender, but didn’t develop aMCI/AD during study.) The researchers took periodic blood samples from the participants and identified 10 metabolites that had similar levels in individuals with aMCI/AD and in people who developed aMCI/AD during the study, but different levels in the people who didn’t develop aMCI/AD.

Specifically, the metabolites (or biomarkers) identified (using tandem mass spectrometry) were variants of phosphatidylcholine, lysophosphatidylcholine, and acylcarnitines. These are phospholipids, which are lipids (i.e., fat molecules) that play key roles in the structure and function of the membranes of cells (which surround cells). Patients who had aMCI/AD, or developed aMCI/AD, had lower levels of these 10 metabolites compared to people who didn’t develop aMCI/AD during the study.

(The researchers also checked for changes in the levels of apolipoprotein E [APOE], since it’s well-known to be a genetic risk for developing AD, but no clear correlations were seen.)

It’s important to keep in mind that blood tests like this not only help improve the diagnosis of disease, but they usually also help us better understand what causes the disease and how it progresses. This study also helps emphasize the importance of applying a variety of techniques to tackle a problem – many Alzheimer’s tests have relied on genetics, but clearly developing biomarker detection tests using blood samples is quite important to pursue.

For further reading:

• Mark Mapstone et al.’s article “Plasma phospholipids identify antecedent memory impairment in older adults” in Nature Medicine
• Tracy Vence’s article “Biomarkers Predict Future Cognitive Impairment“
• Teisha J. Rowland’s book Biology Bytes: Digestible Essays on Stem Cells and Modern Medicine