Published May 16, 2025 2 min read

# FDA clears the first blood test for Alzheimer’s disease

## The short version

The first FDA-cleared Alzheimer's blood test can classify amyloid status about as well as a spinal tap, but only in people who already have cognitive symptoms. It is not a screen for healthy APOE4 carriers. A positive result is biology, not a diagnosis and not a destiny.

By the OutliveAPOE4 editorial team. [How we research & source](/methodology).

On May 16, 2025 the FDA cleared the first blood test to help diagnose Alzheimer’s disease: the Fujirebio Lumipulse plasma **p-tau217 / amyloid-beta 42 ratio**. p-tau217 is a phosphorylated tau-protein fragment used as a marker of Alzheimer-related biology. The test is for adults **55 and older who already have cognitive symptoms**. A blood draw now does work that used to need a PET scan (positron emission tomography, imaging that uses a radioactive tracer to map a biological process) or a spinal tap.

A positive biomarker is not by itself a dementia diagnosis. The [blood-biomarker evidence review](/topics/blood-based-biomarkers-alzheimers) explains p-tau and confirmatory testing; use the [early-detection guide](/topics/mild-cognitive-impairment-and-early-detection) for the practical sequence when symptoms are the concern.

The number that makes this real: p-tau217-based tests classify brain amyloid status with roughly **90 to 95% accuracy**. In the clearance data, the test matched amyloid PET or spinal-fluid results about **92% of the time for positives and 97% for negatives**, which puts a simple blood test on par with far more invasive ones.

Why this matters for a carrier: it makes amyloid testing cheaper and far less invasive, so getting clarity during a symptomatic workup gets easier. But read the result carefully. A positive reflects Alzheimer’s biology, not a diagnosis on its own and not your destiny, and the test is meant to support a clinical evaluation, not replace it.

The honest caveat, and the most important one for carriers: this was cleared for adults who have symptoms, not as a screen for healthy people. Testing an asymptomatic carrier is a different decision with real psychological stakes and no current treatment to change.

We cover what these tests can and cannot tell you in our deep dive on [blood-based biomarkers for Alzheimer’s](/topics/blood-based-biomarkers-alzheimers). A 2025 imaging study also found that APOE4 carriers, especially people with two copies, may show tau-PET changes at a lower blood p-tau217 level than non-carriers. That is a specialist-context finding, not a screening invitation, in [APOE4 lowers the p-tau217 threshold for tau spread](/topics/apoe4-ptau217-tau-threshold). Primary source: FDA, 2025.

## Source & references

1.  [FDA, 2025](https://www.fda.gov/news-events/press-announcements/fda-clears-first-blood-test-used-diagnosing-alzheimers-disease)

## Related deep dives

-   [Blood-based biomarkers for Alzheimer’s: the coming shift For years, confirming Alzheimer’s biology meant a spinal tap or a PET scan. Blood tests are starting to change that. What they measure, where they stand, and the real caveats.](/topics/blood-based-biomarkers-alzheimers)
-   [Mild cognitive impairment & early detection Normal aging, mild cognitive impairment, and dementia are different things. How to tell them apart, what MCI does and doesn’t predict, and when to see a doctor.](/topics/mild-cognitive-impairment-and-early-detection)
-   [Anti-amyloid drugs (lecanemab, donanemab) and what they mean for carriers A new class of Alzheimer’s drugs can modestly slow decline, but APOE4 carriers, especially homozygotes, face higher rates of a key side effect. How they work and what to weigh.](/topics/anti-amyloid-drugs-and-apoe4)