Early Diagnosis of Alzheimer’s Disease with a Blood Test

Alzheimer’s disease, which mostly occurs in older people, is the most common form of dementia (cognitive decline). Although Alzheimer’s progresses slowly, it is a disease that cannot be diagnosed at an early age.

However, a highly promising article on the early diagnosis of Alzheimer’s disease was recently shared. An article in the December 2021 issue of Neurology discussed a highly accurate blood test used in the early diagnosis of Alzheimer’s disease. When assessed alongside genetic risk factors, this test enables the disease to be detected in people at risk of Alzheimer’s dementia before any symptoms are observed, with accuracy of up to 93%.

Washington University School of Medicine developed this blood test, which was used in a study involving about 500 patients from three continents. It proved highly successful in detecting early signs of Alzheimer’s disease and also provided further evidence that the test should be considered for routine screening.

The Advantage of a Blood Test over Standard Diagnosis

The method currently used as the gold standard for diagnosing Alzheimer’s disease is evaluation of the brain through radioactive brain scanning (PET). However, the average cost per scan is quite high. Another commonly used test analyzes levels of amyloid-beta and tau proteins in cerebrospinal fluid. Both its cost and the need to insert a needle in the lower back may make this a procedure some patients are unwilling to tolerate.

Researchers wanted to develop a low-cost, easily accessible blood test for Alzheimer’s as an alternative to the expensive and difficult methods used to assess the presence and progression of the disease in the brain. Ultimately, the blood test developed by Bateman and colleagues enabled an assessment of whether amyloid plaques had begun to accumulate in the brain, based on the ratio of the levels of amyloid beta proteins Aβ42 and Aβ40 in the blood. The blood test even achieved this with a high success rate.

Accuracy of the New Blood Test

To confirm the test’s accuracy, the researchers applied it to blood samples taken from people enrolled in ongoing Alzheimer’s research in the United States, Australia and Sweden. The Aβ42/Aβ40 blood test was confirmed to provide highly accurate and consistent results for people with and without memory loss in all three studies.

When blood amyloid levels were combined with another important Alzheimer’s risk factor (the presence of the APOE4 genetic variant), the blood test’s accuracy was observed to be 88% compared with brain imaging and 93% compared with a spinal tap.

Bateman, in a statement about using the blood test they had developed, said: “This blood test provides major support for Alzheimer’s research and diagnosis, greatly reduces the time and cost of identifying patients for clinical trials, and encourages the development of new treatment options ”. “As new drugs become available, a blood test could identify who may benefit from treatment, including people in the very early stages of the disease.”

- Related topic: What healthy lifestyle habits reduce the risk of Alzheimer’s?