Memory complaints show up in clinics every day. Today, about 57 million people live with dementia worldwide, and Alzheimer’s disease causes most cases.
Doctors rely on interviews, brief cognitive checks, and brain scans when available. A clinically available blood test now offers another option that is simple, fast, and accurate.
Flagging Alzheimer’s in blood
The research team was led by Sebastian Palmqvist at Lund University in Sweden. Their goal was clear: make an accurate test that a regular clinic can use to flag Alzheimer’s biology in people with memory concerns.
In a prospective study of 1,213 patients seen in both family practices and specialty memory clinics, a serum panel correctly identified Alzheimer’s pathology about 88 to 92 percent of the time.
That performance was on par with the accuracy seen when samples were analyzed in batches or as they arrived, which matches how clinics actually work.
The test looks for a specific biomarker in plasma called phosphorylated tau 217, often shortened to p-tau217. It also reads the ratio of amyloid beta 42 to amyloid beta 40, two forms of a protein linked to plaques in Alzheimer’s disease.
These measurements rise or fall in characteristic ways when Alzheimer’s pathology is present. By combining them, the test gives a single probability score that tracks the biology behind memory loss, not just the symptoms.
Help for primary care doctors
“Primary care doctors’ accuracy in identifying Alzheimer’s disease was 61 per cent, while specialist physicians were correct 73 per cent of the time,” added Sebastian Palmqvist, Associate Professor of Neurology at Lund University and consultant at Skåne University Hospital.
The team compared the test’s performance with doctors’ best clinical judgment before any biomarker results were known and those numbers show why an easy lab test can help the first clinicians who see most patients.
Earlier and more accurate classification steers people to the right next step. It also reduces unnecessary referrals for expensive imaging when the blood test rules out Alzheimer’s biology.
Inside the APS2 score
The lab algorithm, sometimes called APS2, blends the p-tau217 percentage with the amyloid ratio to estimate the chance of amyloid positivity in the brain. Ratios help account for unrelated medical factors that can nudge a single marker up or down.
Independent research has shown that percent p-tau217 in blood closely matches the clinical performance of Food and Drug Administration (FDA) cleared cerebrospinal fluid tests for detecting Alzheimer’s pathology. Accuracy climbs even higher when labs use two cutoff values, one to rule in and one to rule out.
Clinicians will still need other information in some cases. A subgroup will land in an intermediate zone, which is a cue to order a PET scan or repeat testing rather than guess.
How this fits with current treatments
Treatments that target amyloid require proof of amyloid biology before they start. The FDA granted traditional approval for lecanemab, marketed as Leqembi, for early symptomatic Alzheimer’s treatment.
The agency also approved donanemab, now sold as Kisunla, for adults with early symptoms and confirmed amyloid pathology. As access to these drugs grows, fast triage in regular clinics becomes more important.
“The test is already available in the USA and is likely to become available in many other countries soon. Initially, it will mainly be used in specialist memory clinics, and it may take approximately one to two years to implement guidelines and training in primary care,” concluded Oskar Hansson, Professor of Neurology at Lund University and senior consultant at Skåne University Hospital.
A blood draw in a familiar clinic setting lowers the barrier for people who cannot travel far or wait long.
Alzheimer’s, blood, and healthcare
A routine blood test is less invasive than a cerebrospinal fluid tap and easier to schedule than advanced imaging. Results can arrive quickly, which helps families move from uncertainty to a clear plan.
An accurate negative result can spare people from months of worry and unnecessary tests. A positive result, combined with a clinical assessment, helps providers arrange the right counseling, safety steps, and referrals.
This test does not replace a full evaluation. Memory changes can come from depression, sleep problems, medications, or other neurological diseases, so clinicians still need to take a careful history and examine the patient.
No test is perfect. A small fraction of results will fall between the lower and upper cutoffs, and that gray zone is best handled with follow up testing or specialty referral.
Local policies will shape how primary clinics use the assay alongside cognitive exams and imaging. Training and clear workflows will help teams decide when to test, how to interpret results, and when to refer.
Researchers will keep studying how comorbid conditions, age, and disease stage affect performance. Automated platforms and standardized reporting should make it easier for labs to deliver consistent results.
The study is published in JAMA.
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