A diagnostic Alzheimer’s blood test that can detect the neurodegenerative disease in pre-symptomatic stages is a dream chased by scientists for decades. But recent developments give hope that the breakthrough be possible — and come sooner than anyone thought.
For years, the only way to diagnose Alzheimer’s was through the use of neuroimaging, i.e., a PET scan, or by analyzing cerebrospinal fluid. These highly invasive tests are expensive and typically only done on symptomatic people. Doctors can only request these tests after the cellular destruction of brain tissue has occurred.
Most people with cognitive complaints are referred to a specialist who reviews the assessment, then authorizes the tests. This process delays the necessary therapy needed to slow down the progression of the disease.
Alzheimer’s disease has molecular hallmark that signify the presence or close-onset of the disease.
Amyloid-beta and Tau are proteins whose abnormal buildup in the brain is associated with the disease. These molecules then spill over into the cerebrospinal fluid and blood.
Promising Studies for Early-Detection Alzheimer’s Blood Tests
For over a decade, researchers have been looking for non-invasive ways to detect Alzhimer’s by testing blood for these proteins. Initial studies found detecting low levels of the relevant proteins in the blood difficult and unreliable.
However, a new study published by Drs. Sebastian Palmqvist and Oskar Hansson from Lund University in Sweden show promising results regarding the effectiveness of the PrecivityAD2 test.
PrecivityAD2 measures the ratio of two forms of amyloid beta along with a specific type of tau called plasma phosphorylated tau 217 (p-tau217). In a previous study, the researchers established the concentration levels of these proteins required to diagnose Alzheimer’s. Researchers compared the results of the blood test against those obtained from a PET scan, a CSF test, and a standard clinical evaluation performed by a doctor.
The results confirmed the validity of the blood test, with an accuracy of 88% to 92% in predicting Alzheimer’s. In fact, the blood tests proved more accurate than standard clinical evaluations, which only had an accuracy between 61% and 73%. Further testing showed that measuring the p-tau217 alone drove similar results as using both proteins.
These results raise hope that blood tests for the early detection Alzheimer’s are on the near-term horizon.
Alzheimer’s treatment is most effective when started early in the disease’s progression. While current therapies have clinical benefits, they cannot regenerate lost brain cells. Instead, they slow the progression of the disease, making these blood tests all the more critical. Alzheimer’s has an approximately two-decade long pre-symptomatic phase where the amyloid builds up into plaques on the brain.
Early Detection, Better Treatments
If treatment can be delivered early — before the onset of neurodegeneration — could the development of Alzheimer’s be prevented?
This is the question the Phase-3 clinical trial, known as AHEAD 3-45, is tasked to answer.
Launched in 2020, AHEAD 3-45 seeks to test the efficacy and safety of Lecanemab, a drug developed to prevent cognitive decline in individuals with preclinical Alzheimer’s disease. This trial could prove revolutionary and change the course of treatment.
“We see this as a major step towards global clinical implementation of an Alzheimer’s blood test,” Dr. Oskar Hansson says. “The next steps include establishing clear guidelines for how an Alzheimer’s blood test can be used in clinical practice, preferably by implementing these tests first in specialist care and then in primary care. This work is currently ongoing.”
The PrecivityAD2 test has yet to be approved by the FDA or covered by insurance, but it is available in the USA.
Related: FDA Approves Kisunla, A First-of-Its-Kind Alzheimer’s Drug
