For years, confirming Alzheimer’s meant a costly brain scan or an uncomfortable spinal tap. Now a blood draw can tell clinicians, with about 90 percent accuracy, whether the brain changes of Alzheimer’s are likely present in a person who is already noticing memory or thinking trouble.
In a 2024 JAMA study led by Sebastian Palmqvist and Oskar Hansson, 1,213 people with memory or thinking symptoms in Swedish primary care and memory clinics gave blood. A score built from p-tau217, a protein fragment that drifts into the blood as Alzheimer’s takes hold, together with an amyloid marker identified Alzheimer’s pathology correctly about 91 percent of the time. When primary care doctors judged the same cases with their usual tools, they were right 61 percent of the time, and specialists 73 percent. A follow-up in Nature Medicine in 2025, using a fully automated lab platform across five cohorts, found similar strength.
Why a clear answer matters
An accurate answer changes what a family can do. It can rule Alzheimer’s in or, just as valuably, rule it out, pointing toward the reversible causes of memory trouble that a doctor can treat. It opens the door to treatments that work best when started early, and it gives a family time to plan, to put the modifiable risks to work, and to make choices while the person at the center can still help make them. Dread thrives on the unknown; clarity gives a family something to do.
A clear answer turns dread into a plan.
How to think about it
If memory has become a worry, this is worth raising with a clinician, who can say whether the blood test fits the situation and how to read the result. It pairs naturally with the search for treatable causes we wrote about in the curable kind of forgetting, since the first job is always to sort what can be fixed from what cannot.
A few limits keep this in proportion. The test shows whether Alzheimer’s changes are likely present in someone who has symptoms, and it does not forecast who will develop the disease. A small share of results land in an uncertain zone that needs more testing. A positive result is a strong signal that a clinician interprets alongside the whole picture. Spinal fluid and brain scans already offered accurate answers, and a blood draw makes them far easier to reach. Knowing carries real emotional weight, so whether and when to test is a personal choice, best made with good counsel. What stands is a genuine step forward: families can now reach an early, trustworthy answer more easily, and with it the power to act sooner.