Memory issues are common in clinics today, with around 57 million people affected by dementia globally, primarily due to Alzheimer’s disease.Doctors typically conduct interviews, cognitive assessments, and brain imaging when possible. However, there’s now a blood test available that is straightforward, quick, and reliable.
Detecting Alzheimer’s Through Blood Tests
The research team, led by Sebastian Palmqvist from Lund University in Sweden, aimed to develop an effective test that regular clinics could use to identify Alzheimer’s biology in patients experiencing memory issues.
In a study involving 1,213 patients from both family practices and memory clinics, the serum panel accurately pinpointed Alzheimer’s pathology 88 to 92 percent of the time. This accuracy aligns with the performance seen when samples are tested in batches or as they come in, which reflects standard clinical practices.
The test identifies a specific biomarker in plasma known as phosphorylated tau 217 (or p-tau217). Additionally, it analyzes the ratio of amyloid beta 42 to amyloid beta 40, two protein variants associated with Alzheimer’s plaques.
These biomarkers fluctuate in distinct patterns when Alzheimer’s pathology is present. By merging these indicators, the test generates a single probability score that reveals the underlying biology of memory loss, rather than just the symptoms.
Support for Primary Care Physicians
According to Palmqvist, primary care physicians tend to identify Alzheimer’s disease accurately about 61 percent of the time, while specialists achieve a 73 percent accuracy rate. The test’s results, compared to clinicians’ initial judgments without biomarker information, highlight the value of this straightforward lab test for primary care professionals, who often see the initial cases.
Timely and precise classification directs patients to appropriate next steps and can decrease unnecessary referrals for costly imaging if the blood test indicates no Alzheimer’s pathology.
The Details of the APS2 Score
The lab algorithm, referred to as APS2, combines the p-tau217 percentage with the amyloid ratio to assess the likelihood of amyloid presence in the brain. These ratios help mitigate impacts from unrelated medical factors that might skew a single marker.
Research indicates that the percentage of p-tau217 in blood closely parallels the efficacy of FDA-approved cerebrospinal fluid tests for detecting Alzheimer’s pathology. The accuracy tends to improve with the implementation of two cutoff values—one for ruling in and another for ruling out.
In some cases, additional information may be necessary. For certain patients who fall into an intermediate category, further tests like PET scans might be needed instead of guessing.
Integration with Current Treatments
Treatments that target amyloid require confirmation of amyloid biology beforehand. The FDA has recently approved lecanemab, branded as Leqembi, for early symptomatic Alzheimer’s, as well as donanemab, now known as Kisunla, for adults showing early symptoms along with confirmed amyloid pathology. As access to these therapies expands, efficient triage in primary care clinics will become increasingly significant.
According to Oskar Hansson, a professor of neurology at Lund University, the test is already available in the U.S. and is expected to become accessible in other countries soon. Initially, it will be predominantly used in specialized memory clinics, and rolling out guidelines and training for primary care may take one to two years.
A blood draw in a familiar clinic setting minimizes barriers for individuals who might struggle to travel or wait long periods.
Alzheimer’s, Blood Tests, and Health Care
A routine blood test is less invasive than a cerebrospinal fluid draw and simpler to schedule than sophisticated imaging, often yielding quick results that help families transition from uncertainty to actionable plans.
An accurate negative result can alleviate months of anxiety and unnecessary tests. Conversely, if results are positive, accompanied by a clinical evaluation, it aids healthcare providers in organizing appropriate counseling, safety measures, and referrals.
This test isn’t a substitute for a comprehensive evaluation. Memory changes may also stem from depression, sleep issues, medications, or other neurological disorders, so it remains essential for clinicians to gather a thorough history and conduct a patient examination.
No test is infallible, and a small number of results might land in a gray area between cutoffs. Such cases are ideally managed with follow-up testing or referrals to specialists.
The application of this test will be influenced by local policies, determining how primary care clinics use it alongside cognitive assessments and imaging. Training and clear operational procedures will assist teams in deciding when to administer the test, interpret findings, and determine when referrals are necessary.
Future research will continue to explore how factors like comorbid conditions, age, and disease stage affect the test’s performance. Standardized reporting and automated platforms should streamline labs’ ability to provide consistent results.
The study appears in JAMA.
