PrecivityAD2, a blood test that estimates amyloid-plaque risk in adults with cognitive symptoms, is cleared as an aid to specialist assessment in 2026. For memory clinic patients, strong positive and negative results align closely with PET or spinal fluid findings.
An intermediate result band still leaves about one in six patients needing further testing. The test applies to adults age 40 and older who already have signs of impairment. It does not replace history, examination, or clinician judgment, and it is not meant for routine screening.
Medical information disclaimer: This article is for general educational purposes only and does not provide medical advice, diagnosis, or treatment. Always consult a physician or other qualified health professional about symptoms, medications, tests, or treatment decisions.
Table of Contents
- What the blood test measures
- How well it matched PET and spinal fluid
- Who still needs more testing
- How a memory clinic uses the result
What the blood test measures
The test measures two plasma ratios linked to Alzheimer pathology: Aβ42/40 and p-tau217 to non-p-tau217. According to NeurologyLive coverage, high-resolution mass spectrometry produces the results, which are combined into an Amyloid Probability Score 2 from 0 to 100.
A higher score means a higher likelihood of brain amyloid on PET or spinal fluid testing. A lower score means a lower likelihood. The number guides next steps, but a clinician must read it with symptoms and exam findings.
How well it matched PET and spinal fluid
In a 1,142-person validation group with cognitive symptoms, researchers compared blood results against amyloid PET or cerebrospinal fluid. According to NeurologyLive coverage, a Positive result had 97.6% positive predictive value, while a Negative result had 93.1% negative predictive value.
That means most clear positives and clear negatives agreed with the reference test. Performance also held steady across age groups and 12 chronic conditions, including chronic kidney disease, atrial fibrillation, and diabetes. Those conditions often distort blood markers, so steady performance matters for older clinic patients.
Who still needs more testing
About 17.3% of results fell in a middle band called likely positive. In that group, positive predictive value was 77.3%, so the result alone cannot settle the question.
Practical Neurology reports the test is cleared only as an adjunct to assessment by professionals experienced in cognitive-impairment evaluation, not as screening or a stand-alone diagnosis, in the Practical Neurology report. For patients in the middle band, the usual path is added testing with PET or spinal fluid. Even outside that band, the blood result joins clinical findings rather than replacing them.
How a memory clinic uses the result
For specialized workups, the Alzheimer Association approach uses qualified blood markers as triage. According to Healio reporting of Association guidance, a negative result helps rule out amyloid pathology, while a positive result is confirmed with PET or spinal fluid testing. A visit often follows this order: Bring a symptom timeline, a medication list, and a family member who sees daily function.
- Review cognitive symptoms, onset, daily impact, medications, and medical history.
- Order PrecivityAD2 when amyloid status would change care planning.
- Confirm positives and intermediate results with PET or spinal fluid testing.
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