PrecivityAD2 is a blood test that aids Alzheimer's evaluation by measuring blood signals tied to amyloid pathology, abnormal protein buildup in the brain. Memory clinic patients can bring questions about eligibility, score meaning, follow-up testing, and treatment decisions.
WashU The Source reports the FDA cleared C2N Diagnostics' PrecivityAD2 on August 19, 2026 the FDA clearance announcement. Clearance covers adults aged 40 and older with signs or symptoms of cognitive impairment. Use it as an adjunct, not a stand-alone answer.
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 does adjunct mean?
- Are you in the intended group?
- What do your numbers mean?
- What comes after the blood draw?
What does adjunct mean?
Practical Neurology notes FDA labeling requires use with clinical assessment by clinicians experienced in cognitive-impairment evaluation the FDA labeling summary. It identifies amyloid pathology and is not screening or a stand-alone diagnosis. Your clinician pairs the blood result with history, exam, cognitive testing, and other possible causes. The blood signal alone does not name the cause of memory change.
Ask how your clinical findings and blood result fit together. A positive result points toward amyloid buildup, while a negative result points away from it. Ask what each outcome would change for your care plan. Ask what would stay uncertain either way.
Are you in the intended group?
The intended visit is an evaluation for cognitive impairment, not a routine check. The clinician decides whether memory symptoms, timeline, medications, sleep, mood, and medical issues make testing useful. Bring a symptom timeline and medication list.
Ask these fit questions at the visit: BrightFocus Foundation frames the practical check as whether the clinic uses an FDA-cleared test performed at C2N's laboratory. If the answer is no, ask which test is used instead. If yes, ask how that clinic handles borderline cases.
- Do my signs place me in the test's intended use?
- Will a clinician experienced in cognitive-impairment evaluation interpret the result with my exam?
- Is the sample sent to C2N's laboratory using the FDA-cleared method?
- What other causes will you rule out first?
What do your numbers mean?
WashU The Source reports PrecivityAD2 uses high-resolution mass spectrometry to quantify plasma amyloid-beta 42/40 ratio and percent phosphorylated tau-217. Amyloid-beta 42/40 is a ratio of two blood protein fragments. Phosphorylated tau-217 is a modified tau protein linked to Alzheimer's changes. Mayo Clinic Laboratories lists an Amyloid Probability Score 2 from 0-100, with 0-47 negative and 48-100 positive the test catalog entry.
It also lists component cutoffs of Abeta42/40 at 0.095 and percent p-tau217 at 4.2%. Higher scores mean higher likelihood of brain amyloid pathology. Ask which part drove your score and how close it sits to the cutoff. A score near 47 or 48 deserves extra caution. Ask whether repeat testing, records review, or added testing would clarify it.
What comes after the blood draw?
WashU The Source reports validation studies found over 90% accuracy for brain amyloid pathology, comparable to spinal-fluid testing and amyloid PET imaging, with a less-invasive blood draw. Healio Neurology reporting C2N release cites 97.6% positive predictive value for a positive result and 93.1% negative predictive value for a negative result in its FDA-clearance study population. Predictive value means how often that result matched the expected amyloid status in that study group. Alzheimer Europe summarizing the Alzheimer's Association July 2025 guideline says blood-biomarker tests with at least 90% sensitivity and 75% specificity should be used only as triage in specialty memory care.
Positive results need confirmation by spinal-fluid testing or PET. Sensitivity is ability to find true cases, while specificity is ability to rule out non-cases. Ask what confirmation and care path follow each result: BrightFocus Foundation frames the same next-step check as asking what a positive or negative APS2 would change and whether PET or spinal-fluid confirmation and treatment eligibility review follow. Ask who will call with results, how soon, and what decision each result triggers.
- Would a positive APS2 lead to PET or spinal-fluid confirmation here?
- Would a negative APS2 stop the search or prompt other workup?
- Will you review treatment eligibility after confirmation?
- Who explains results, when, and in what form?
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