PrecivityAD2, a blood test that estimates likelihood of Alzheimer's-related amyloid buildup, is cleared for adults age 40 and older with cognitive symptoms. It does not by itself diagnose younger-onset Alzheimer's, which still requires clinical assessment and confirmatory workup in primary care. For patients in their 40s to early 60s, the value is earlier direction, not a final label. The sections below explain what the score measures, how well it performs, and what steps make a referral productive.
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 score measures
- How well does it predict amyloid?
- Who fits the cleared use?
- What are the next steps after testing?
What the score measures
Patient Care Online describes PrecivityAD2 as using high-resolution mass spectrometry to measure two plasma ratios, Aβ42/40 and %p-tau217. The test combines them into an Amyloid Probability Score 2 from 0 to 100 for likelihood of amyloid pathology. C2N Diagnostics states the test must be used alongside clinical assessment by professionals experienced in cognitive-impairment evaluation, according to the clearance announcement.
It is not cleared as screening in healthy people or as a stand-alone diagnosis. Amyloid pathology means abnormal protein deposits linked to Alzheimer's disease. A higher APS2 means a higher likelihood that such pathology would appear on PET or spinal-fluid testing.
How well does it predict amyloid?
In a 1,142-person study against PET or spinal-fluid testing, Patient Care Online reported positive results predicted amyloid pathology 97.6% of the time, according to the test performance summary. Negative results correctly ruled it out 93.1% of the time.
About 17.3% of people fell into a middle likely-positive group with lower predictive value, 77.3%. In symptomatic cohorts in primary and specialty care, AJMC reported accuracy of about 88% to 92% against PET or spinal-fluid testing, according to the primary-care analysis. The comparison suggests a single blood draw can perform comparably to a scan or spinal tap for triage, not replacement.
Who fits the cleared use?
The cleared use is narrow. Clearance covers adults age 40 and older with signs of cognitive impairment, as announced by C2N Diagnostics. The Alzheimer's Association blood-biomarker guideline from 2025 applies only to patients with objective impairment seen in specialty or memory-clinic care.
It sets high accuracy bars for triage use and even higher bars to replace PET or spinal-fluid testing. The Social Security Administration defines young-onset Alzheimer's as diagnosis before age 65, accounting for about 5% to 10% of cases, according to the disability evaluation guidance. It states there is no single diagnostic test for this group.
- age 40 or older
- signs of cognitive impairment, not routine screening
- evaluation by a clinician experienced in cognitive assessment
- plan for follow-up testing and care planning
What are the next steps after testing?
For younger adults, workup still requires history, cognitive testing, neurologic examination, imaging, and laboratory testing, as described by the Social Security Administration. A blood result fits inside that sequence, rather than ending it.
For primary-care use in 2026, AJMC described counseling that the FDA-cleared kit was expected later in 2026 with the CLIA laboratory version available meanwhile. The practical path is referral for confirmatory workup and care planning, especially for younger patients. Bring a dated symptom timeline and medication list to that visit.
- bring a dated timeline of memory, language, work, and driving changes
- bring medications, sleep, mood, alcohol, and medical history
- ask whether PET, spinal-fluid testing, or specialty referral is needed
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