A new study has found that a blood test can determine whether memory loss is due to Alzheimer’s disease with a 90% accuracy rate. This blood test could revolutionize how early cognitive decline is diagnosed and treated, providing a much-needed alternative to current methods.

Current Challenges in Diagnosing Alzheimer’s

The study highlights a significant gap in accuracy between the new blood test and the diagnoses made by medical professionals. Neurologists and memory specialists currently have an accuracy rate of 73% when diagnosing Alzheimer’s, while primary care doctors manage only 61% accuracy. These rates highlight the difficulty of accurately diagnosing Alzheimer’s using current methods, which often include short interviews, brief cognitive tests, and CT scans of the brain.

How the Blood Test Works

The blood test measures levels of a protein called plasma phosphorylated tau 217 (p-tau217). This protein is an indicator of amyloid plaques in the brain, which are closely associated with Alzheimer’s. According to Dr. Sebastian Palmqvist, a neurologist and associate professor at Lund University in Sweden, p-tau217 levels are significantly higher in individuals with Alzheimer’s compared to those without the disease.

The study found that a similar p-tau217 test can be up to 96% accurate in identifying elevated levels of beta-amyloid and up to 97% accurate in identifying tau proteins. The combination of these tests provides a clear picture of Alzheimer’s presence.

The new study used a combination of p-tau217 with another blood biomarker test that measures the amyloid 42/40 ratio. This combination, known as the amyloid probability score, was the most predictive in diagnosing Alzheimer’s.

Potential Impact of Blood Tests on Alzheimer’s Diagnosis

Dr. Maria Carrillo, the chief science officer of the Alzheimer’s Association, emphasized the potential impact of a blood test that could be used in a primary care physician’s office. Such a test could function like a cholesterol test for Alzheimer’s, drastically changing the speed and accuracy of diagnosis.

The blood test could also play a crucial role in accelerating Alzheimer’s research and drug development. Early detection through a simple blood test could allow patients to start lifestyle changes and treatments earlier, potentially slowing the progression of the disease.

The Science Behind the Blood Test

The p-tau217 peptide is unique because it can only be detected when amyloid plaques are present in the brain. This means that the test indirectly measures amyloid presence by identifying the neuronal damage caused by tau proteins early in Alzheimer’s development.

Although p-tau217 doesn’t directly measure amyloid, its accuracy has been supported by PET (positron emission tomography) scans that visually confirm amyloid in the brain. This biomarker is particularly valuable because if amyloid isn’t present, it rules out Alzheimer’s, while elevated tau levels suggest another type of dementia.

Tau tangles are also found in other neurological diseases like frontal lobe dementia (FTD), where they cause different symptoms. In FTD, tau tangles affect the brain’s frontal lobe, leading to behavioural and emotional changes, with memory loss occurring much later.

Implications for Current Treatments

The newest drugs for dementia, such as lecanemab and donanemab, target beta-amyloid and are less effective in individuals with advanced tau pathology. Therefore, early detection of amyloid deposits can be critical for starting treatments that may be more effective in the early stages.

Amyloid plaques can begin to accumulate decades before symptoms appear, even as early as a person’s 30s or 40s. Early diagnosis could be vital for lifestyle modifications and preventive treatments with medications.

Study Details

Published in the journal JAMA Neurology, the study involved 1,213 participants with an average age of 74. Each participant underwent cognitive evaluations in primary care and speciality clinics in Sweden.

Blood tests using p-tau217 were conducted, and the results were combined with beta-amyloid 40/42 measurements to create a final score. The blood test’s accuracy was confirmed through spinal fluid taps, the current gold standard for diagnosing Alzheimer’s alongside amyloid PET scans.

The study results were then compared to diagnoses made by Swedish primary care doctors and specialists, revealing the blood test’s superior accuracy.

The Future of Alzheimer’s Diagnosis

While blood tests for Alzheimer’s aren’t expected to be available in doctors’ offices immediately, their potential to revolutionize diagnosis is significant. Additional research is needed to confirm the positive results seen in studies, and guidelines for physician use must be established.

Dr. Richard Isaacson, a preventive neurologist, stressed that although blood tests are not yet definitive, they are promising tools for early diagnosis and response to risk-reducing interventions.

Taking Preventive Measures

While waiting for the widespread availability of blood tests, individuals can take proactive steps to prevent or slow cognitive decline. Research supports regular exercise, a Mediterranean-style diet, and addressing vascular risk factors like high blood pressure, high cholesterol, and diabetes as effective measures.

The development of highly accurate blood tests for Alzheimer’s marks a transformative moment in dementia diagnosis and treatment. With continued research and development, these tests could provide a powerful tool for early detection and intervention, offering hope for individuals at risk of Alzheimer’s disease.

These are exciting times in Alzheimer’s research, as the potential for early diagnosis and effective treatment becomes increasingly attainable.