According to statistics, one in five women and one in 10 men develop dementia due to AD (Alzheimer’s disease).
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The story so far: Researchers have developed a new blood test to detect Alzheimer’s disease that helps diagnose the disease even at the early stage of mild cognitive impairment. Scientists at Lund University in Sweden have shown that PrecivityAD2, a new blood test, is about 90% accurate in identifying AD in people experiencing cognitive symptoms. The paper ‘Blood Biomarkers to Detect Alzheimer Disease in Primary Care and Secondary Care’ by Sebastian Palmqvist et al was published in the July 28 edition of peer-reviewed journal JAMA.
Why are practitioners excited about the test?
According to statistics, one in five women and one in 10 men develop dementia due to AD (Alzheimer’s disease). Individuals with cognitive symptoms are first seen in primary care, with a minority being referred to secondary care, authors of the article pointed out. Further they added that symptomatic AD is misdiagnosed in 25% to 35% of patients treated at even specialised clinics and likely even more patients treated in primary care.
For long, a blood test has been the Holy Grail for diagnosis of AD, since even current, modern methods of diagnosis involve very expensive and complex amyloid or Tau Positron Emission Tomography (PET) scans. The other alternative is to draw cerebrospinal fluid via a painful procedure, lumbar puncture. “The big goal is a serum study,” explains neuropsychiatrist E.S. Krishnamoorthy of Buddha Clinic who has a special interest in dementia, whose most prevalent type is Alzheimer’s disease. This blood test comes as close to the target as possible, and in that sense will make the diagnosis of AD very simple. Blood tests will not only reduce the costs of diagnosis, but also simplify the diagnostic procedure — involving as it does, just drawing of blood. There have been a few commercial attempts that went live before this test, but the current study has provided some definitive results.
In a statement to Medscape Medical News, Howard Fillit, co-founder and chief science officer of the Alzheimer’s Drug Discovery Foundation, says: “Blood tests are revolutionising Alzheimer’s detection, diagnosis and ultimately treatment.” He believes that these tests will “soon replace more invasive and costly PET scans as the standard of care and serve as the first line of defence in diagnosing the disease.” Dr. Fillit adds: “After many years of research, the field is in a place where we have novel biomarkers and diagnostics to support a diagnosis, the way cholesterol is used to help detect heart disease.”
What does the test do?
According to Medical News Today, the test works by measuring a combination of two ratios within a blood sample: plasma phosphorylated-tau217 (also called p-tau217) to not-phosphorylated-tau21 and two types of amyloid-beta: AB42 and AB40. Let it suffice for us to understand that both tau and amyloid-beta proteins are currently considered pathological hallmarks of AD.
A total of 1,213 patients were already under evaluation for cognitive decline in primary or secondary care centres between February 2020 and January 2024 in Sweden. Of the participants, 23% had subjective cognitive decline, 33% had dementia, and 44% had mild cognitive impairment. About 50% of participants showed Alzheimer disease pathology through primary and secondary care testing. In comparison to the blood test that had an accuracy of 91%, dementia specialists identified clinical Alzheimer disease with a diagnostic accuracy of 73%, the researchers say in their paper. In primary care, physicians had a diagnostic accuracy of 61%, they add. They argue that this would be an accurate blood test for AD and that it could streamline the diagnostic workup and treatment of AD. The significance is that there are several drugs that work in the early stages of the disease, and an early, cost-effective, simple diagnosis will go a long way for patients, experts say.
How does this impact the future?
Future studies should evaluate how the use of blood tests for these biomarkers influences clinical care, researchers have said in their paper. No doubt the costs will come down, naturally impacting positively on affordability. Availability is the other issue. Dr. Krishnamoorthy says that in India, the diagnostic tools still remain an MRI and a regular PET scan. Amyloid or Tau PET scans are not commercially available yet. He adds that availability of the blood test will happen, but one needs to wait and watch if the test will be accessible to all or if only a few will be able to afford the test, even at reduced rates.
