How Alzheimer’s could be detected early from a blood sample

A team of scientists from the United States and Sweden developed a test that would replace expensive brain scans or lumbar punctures.

When a person is diagnosed with Alzheimer’s, doctors rely on signs and symptoms that appear after the disease has already caused brain damage. That is why research is being done to have tools that allow an easy and precise way to detect this neurodegenerative disorder before the characteristic signs begin.

“Biological markers” or biomarkers are considered to offer one of the most promising avenues for making an earlier diagnosis. In the United States and Sweden, a group of scientists took a step in that direction. They developed a test to detect a new marker of Alzheimer’s neurodegeneration from a blood sample.

The researchers belong to the School of Medicine of the University of Pittsburgh, United States, and the University of Gothenburg, in Sweden, among other institutions; and they have released the details of the test to detect the marker of neurodegeneration in a blood sample through a report published in the specialized magazine Brain.

The biomarker is called “brain-derived tau,” or BD-tau. According to the researchers, this marker exceeds the results of current diagnostic blood tests used to clinically detect Alzheimer’s-related neurodegeneration.

Furthermore, they reported that it is specific for Alzheimer’s disease and correlates well with neurodegeneration biomarkers of the pathology in cerebrospinal fluid.

Currently, to diagnose this disease, doctors use the guidelines established by the National Institute on Aging and the Alzheimer’s Association, in 2011.

These models require the detection of three distinct components of the pathology: the presence of amyloid plaques, tau tangles, and neurodegeneration in the brain. Its registration is made by images or through the analysis of cerebrospinal fluid samples.

“Unfortunately, both approaches suffer from economic and practical limitations,” the researchers said in a statement.

This imposes the need to develop comfortable and reliable biomarkers in blood samples.

Developing simple tools that detect signs of Alzheimer’s in the blood, without compromising quality, is an important step in improving accessibility, said Dr. Karikari.

“The most important utility of blood biomarkers is to improve people’s lives and improve clinical confidence and risk prediction in the diagnosis of Alzheimer’s disease,” he added.

Current blood diagnostic methods can accurately detect abnormalities in plasma amyloid beta and the phosphorylated form of tau, which are two of the three parameters needed to confidently diagnose Alzheimer’s.

But the biggest obstacle to applying the guidelines established in 2011 to blood samples lies in the difficulty of detecting neurodegeneration markers specific to the brain and not influenced by potentially misleading contaminants produced in other parts of the body.

By applying their knowledge of the molecular biology and biochemistry of tau proteins in different tissues, such as the brain, Karikari and his team (along with colleagues at the University of Gothenburg, Sweden), developed a technique to selectively detect BD-tau. This avoids detecting the floating “big tau” proteins produced by cells outside the brain.

The tests showed that the levels of BD-tau detected in blood samples from Alzheimer’s patients by the new assay matched the levels of tau in cerebrospinal fluid and reliably distinguished Alzheimer’s from other neurodegenerative diseases.

BD-tau levels also correlated with the severity of amyloid plaques and tau tangles in brain tissue confirmed by brain autopsy analyses.