Blood test may give early Alzheimer’s warning
Ratios of amyloid beta proteins in a patient’s blood can reveal Alzheimer’s disease decades before symptoms occur
In a recent study of the relationship between Alzheimer’s disease and a protein called amyloid beta, researchers have uncovered a link that could help them create a blood test for the condition that would be less invasive than current methods of diagnosis and give early warning for patients who do not yet have any symptoms of the degenerative disease.
This could have significant real-world benefits for many patients, since current Alzheimer’s diagnoses either rely on PET scanning, which is expensive and not very accessible, or spinal taps – invasive procedures through which fluid is taken from the spine using a hollow needle.
A simple blood test measuring amyloid beta levels in the bloodstream has previously been proposed as a solution to this problem, as this protein has a tendency to manifest in plaque sites that dot the brains of Alzheimer’s patients decades before they develop memory loss and confusion.
Unfortunately, scientific investigations have found that measures of the total level of amyloid beta in the blood do not correlate with the amount created in the brain.
To get around this issue, a research team led by Randall Bateman from Washington University’s School of Medicine in St Louis, decided to measure the levels of three of the protein’s subtypes – amyloid beta 38, 40 and 42 – in patients’ blood to see if any correlated with the amount of amyloid buildup in their brains.
The scientists examined 41 patients over the age of 60 using mass spectrometry to measure the proportion of amyloid subtypes in their blood. 23 of these patients were amyloid positive and showed cognitive impairment, while 18 showed no signs of amyloid build up.
The results of the experiment, which are published in Alzheimer’s and Dementia, showed that levels of amyloid beta 42 relative to amyloid beta 40 were consistently 10 to 15 percent lower in patients with plaque buildup in their brains, indicating that amyloid 42 was being deposited there.
The work of Bateman and his team is a strong step towards understanding one of the two characteristic signs of Alzheimer’s disease, amyloid plaque. If combined with a blood test for the other sign, tangles of brain protein known as tau, the researchers believe amyloid beta tests could be used to help predict and possibly prevent the debilitating mental condition.