A blood test may help in diagnosing Alzheimer’s disease at an early stage. It can assess the levels of protein amyloid-beta in the blood. By using these levels one can check if the brain has a build-up of this protein. A study in the journal “Neurology” has published this finding.
Levels of amyloid-beta in the blood can predict amyloid accumulation in the brain
Alzheimer’s disease is a condition that causes the death of the brain cells. Later on, that can lead to confusion and memory loss. The clumps of the protein amyloid-beta start forming in the brain, twenty years before the appearance of the symptoms.
The research team has reported that analyzing the levels of this protein in the blood has enabled them to predict the protein build up in the brain. The blood test measures the quantity of two forms of amyloid-beta protein (amyloid-beta 42 and amyloid-beta 40), using mass spectrometry.
There is a decrease in the ratio of these two proteins with a raise in amyloid-beta deposits in the brain. Existence of the genetic variant – APOE4 and age are two major risk factors for Alzheimer’s disease.
Combining the protein levels in blood with these two risk factors can increase the accuracy of the blood test by 94%. The research team has also found that the blood test may be more sensitive for detecting early amyloid deposition than a PET brain scan (a gold standard test).
This study involves 158 adults with an age above 50. All but 10 of these adults were having cognitive problems. These 158 adults underwent both, the blood test, and a PET scan for at least one time.
The research team classified the results of these tests as positive or negative. 88% of the time, the results of the blood test of each adult were agreeing with his/her PET scan.
The blood test can detect the early brain changes ignored by the gold standard test
To improve the accuracy of the results, the team also considered a few major risk factors of the disease. Age above 65, can raise the risk of disease by two folds every 5 years. APOE4 – a genetic variant increases the risk by 3 – 5 times.
Gender is also a known risk factor for Alzheimer’s. Two of every three patients of Alzheimer’s are women. Involving these risk factors in the analysis have shown that age and APOE4 were increasing the blood test’s accuracy by 94%. But sex had no significant effect on accuracy.
The team initially concluded the results of few people as false positive. The blood tests for these people were positive while brain scans were negative. But after about four years, some of these people showed positive results on brain scanning.
It suggested that the blood test can detect the early stage of Alzheimer’s, missed by the gold standard test. After the appearance of cognitive symptoms, no therapy can completely heal the patients. So, treatment of the Alzheimer’s should start before arising of any cognitive symptoms.
The use of brain scans for screening people for clinical trials is expensive and time-consuming (may take years). While a blood test may diagnose Alzheimer’s disease at an early stage by screening patients with changes in the brain but no cognitive problems.
Also, the blood test costs less and can screen thousands of people in a month. By reduction in the number of PET scans and use of blood tests, clinical trials for testing a drug can run faster that is a step closer to preventing Alzheimer’s.