PrecivityAD2 is a blood test that aids Alzheimer's evaluation in adults age 40 and older who have cognitive symptoms, used alongside clinical workup. For younger-onset families, its 0-to-100 score signals likely amyloid buildup but does not diagnose Alzheimer's alone. The test measures amyloid and tau signals from one blood draw. Families still need a clinician to place that number beside symptoms, history, exams, and often follow-up testing.
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 the 0-to-100 number mean?
- Why is it an adjunct, not an answer?
- How accurate is it, and what bar should families know?
- Why does this matter for younger-onset families?
- What should you ask at the results visit?
What does the 0-to-100 number mean?
The report gives an Amyloid Probability Score 2. A score of 0 to 47 is negative. A score of 48 to 100 is positive and consistent with amyloid PET positivity, according to the Mayo Clinic Laboratories catalog in Mayo Clinic Laboratories test catalog. Think of negative as lower likelihood of brain amyloid at this time.
Think of positive as higher likelihood that a PET scan would also show amyloid. The number is a probability aid, not a stage or severity grade. A score near the middle deserves careful review. Ask what repeat or confirmatory test the clinic uses when the result conflicts with symptoms.
Why is it an adjunct, not an answer?
PrecivityAD2 was cleared to aid evaluation, not to screen healthy people or give a standalone diagnosis. C2N Diagnostics reports FDA clearance on Aug. 20, 2026 for adults 40 and older with cognitive symptoms, with clinical workup, in C2N Diagnostics clearance notice.
The Alzheimer's Association advises confirming positives with PET or cerebrospinal fluid testing because many commercial blood tests vary and miss accuracy thresholds, as stated in Alzheimer's Association statement. That caution matters for younger adults, where another cause may explain symptoms. Use the result to guide next steps. Do not use it to start, stop, or choose treatment without specialist review.
How accurate is it, and what bar should families know?
External validation in cognitively impaired adults found about 91 percent agreement with amyloid PET, with sensitivity and specificity near or above 90 percent. The 1,142-person study was reported in Alz and Dementia and indexed by PubMed. The Alzheimer's Association guideline from July 29, 2025 sets a high bar.
Only blood tests with at least 90 percent sensitivity and specificity may substitute for PET or spinal-fluid testing, and testing should follow objective impairment and specialist review. Ask the clinic which test version was used. Ask for sensitivity, specificity, and whether local policy still requires PET or spinal-fluid confirmation.
Why does this matter for younger-onset families?
Young-onset Alzheimer's means symptoms before age 65. It accounts for about 5 to 6 percent of cases, reports AJMC, and is often first attributed to depression, burnout, sleep loss, or perimenopause. Problems at work, missed bills, lost words, or unsafe driving often prompt the first serious evaluation.
A blood result can shorten that diagnostic odyssey when paired with exams and history. Paired with clinical assessment, the approach raised primary-care diagnostic accuracy from 65 percent to 93 percent and helped document amyloid pathology often needed for treatment planning, according to AJMC report. Bring job examples, financial errors, and a timeline to the visit.
What should you ask at the results visit?
A short checklist keeps the visit focused on decisions. Bring a partner or relative who sees daily function.
Write down the plan and test dates. Ask how to share results with employers, insurers, or family only as needed.
- What was the exact score, and was it negative or positive?
- How does the score fit symptoms, age, medications, and other causes?
- Do we need PET, spinal-fluid testing, genetics, or referral now?
- What work, driving, safety, and support plans should change next?
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