Alzheimer’s: an ultra-precise blood test with 90% accuracy soon at your GP?

Scientists are constantly working on Alzheimer’s disease, in order to improve the diagnostic tools for this dementia. A new study has just been published in the JAMA Network. It evaluates the effectiveness of a combined test to diagnose the disease through two blood biomarkers.

A combination of biomarkers typical of the disease

For this work, presented on Sunday July 28, 2024 at the annual international conference of the Alzheimer’s Association, in Philadelphia, United States, researchers from Lund University, Sweden, brought together a cohort of 1,213 people with an average age of 74, who underwent cognitive tests.

Among them, 23% had subjective cognitive decline; 44% had mild cognitive impairment and 33% had dementia.

Each volunteer also had a blood test taken to perform this new blood test, based on two biomarkers typical of the disease.

What are these two biomarkers?

The two biomarkers targeted by the scientists are:

• Plasma phosphorylated Tau 217 proteinor p-tau 217, because the Tau protein tends in Alzheimer’s disease to aggregate abnormally in the brains of patients;
• The 42/40 amyloid ratiomeasuring a ratio of two types of amyloid proteins, which accumulate as plaques in the brains of patients.

These two biomarkers have been identified in previous studies as being reliable, to indicate the presence of the disease. In a study published last January, Swedish researchers had also already been able to demonstrate that the presence of p-tau217 was linked to Alzheimer’s disease and that it could be an early marker of the disease.

Similarly, the beta-amyloid marker 42/40 is considered a marker of amyloid plaques in the brain, which is one of the components of the pathophysiology of Alzheimer’s disease.

An accuracy rate of over 90%!

Result: Thanks to this combined blood test, the researchers were able to detect the disease with an accuracy of more than 90%. In comparison, neurologists and other memory experts correctly diagnose it only 73% of the time, and general practitioners only 61% of the time.

To do this, the doctors based their diagnosis on the standard assessment (clinical examination, cognitive tests and CT scan) before seeing the results of the biomarkers. Then, to confirm them, a puncture of the cerebrospinal fluid associated with a positron emission tomography (PET) was performed. This is the only scientific reference method for making the diagnosis currently (apart from the autopsy…).

Towards a blood test that can be carried out by the treating physician?

Both of these tests are expensive, invasive and difficult to access. The aim would therefore be to develop a routine blood test that can be carried out during a consultation with your doctor. “Initially, it will be used primarily in memory clinics, and it may take about one to two years to implement the guidelines and training in primary care.” says Sebastian Palmqvist, associate professor of neurology at Lund University and author of the study.

“Next steps include establishing clear clinical guidelines for the use of the blood test in health care. The test is already available in the United States and will likely soon be available in many other countries. Initially, it will be used primarily in memory clinics, and it may take about one to two years to implement guidelines and training in primary care.” concludes Oskar Hansson, professor of neurology at Lund University.

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