PrecivityAD2, an FDA-cleared blood test for Alzheimer's evaluation, gives an Amyloid Probability Score 2 from 0 to 100 that signals low or high likelihood of brain amyloid. A result alone does not diagnose Alzheimer's and must be read with a clinical evaluation for cognitive impairment.
C2N Diagnostics announced in the FDA clearance notice that the test is cleared for adults age 40 and older with signs of cognitive impairment. That age range matters for younger-onset disease. Primary care patients need clear questions about cutoffs, accuracy limits, and next tests.
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 your 0-100 score mean?
- Why isn't a positive result an Alzheimer's diagnosis?
- Why does the age-40 clearance matter for younger onset?
- What should you ask your primary care doctor next?
What does your 0-100 score mean?
The score combines two blood ratios into one number. It measures plasma Aβ42/40 and p-tau217/non-p-tau217 by high-resolution mass spectrometry. Mayo Clinic Laboratories explains in its test catalog that 0-47 is Negative and 48-100 is Positive. Negative means low likelihood of brain amyloid by PET.
Positive means high likelihood of brain amyloid by PET. A score near the cutoff needs extra care. A 46 and a 49 fall on different sides but are close in value. Ask what your exact number was and how your symptoms fit it.
Why isn't a positive result an Alzheimer's diagnosis?
Amyloid likelihood is only one piece of the puzzle. Memory loss, thinking changes, medicines, sleep, mood, and other medical causes still need review. AJMC, reporting the clearance, notes in its FDA clearance report that labeling requires use with clinical assessment by professionals experienced in cognitive-impairment evaluation. The test is not stand-alone diagnosis.
It is also not for screening without symptoms. That limit protects younger adults in primary care. Early symptoms can have many causes at age 40 to 64. A blood result cannot replace history, exam, cognitive testing, and follow-up.
Why does the age-40 clearance matter for younger onset?
Younger or early-onset Alzheimer's affects people younger than 65. The 40-plus clearance now overlaps that whole primary-care group. This overlap can shorten the path to answers for working-age adults. Job performance, driving, parenting, and financial choices may already feel strained.
An amyloid result helps frame urgency without settling the cause. It does not mean every 40-year-old with brain fog needs testing. Testing applies during an Alzheimer's evaluation for cognitive-impairment signs. Ask whether your symptoms meet that starting point.
What should you ask your primary care doctor next?
Bring your exact score, symptom timeline, medicines, and family history. Ask how the result changes your working diagnosis and referral plan. Ask whether specialty care, cognitive testing, or brain imaging is next.
The Alzheimer's Association states in its 2025 guideline release that qualifying blood tests act as triage for cognitively impaired specialty-care patients, with positive results confirmed by CSF or amyloid PET. That model fits primary care too. Write down the answers before you leave. Keep one contact for follow-up results and referrals.
- Was my sample result Negative or Positive at the 47/48 cutoff?
- What else could explain my symptoms besides amyloid?
- Do I need referral for specialty review, CSF testing, or amyloid PET?
- What safety, work, and driving steps should I take while waiting?
You Might Also Like
- How 2026 Tau Imaging News May Affect Alzheimer’s Workups: How Primary Care Patients Can Compare Testing Options
- Day-One Subcutaneous Leqembi for Early Alzheimer’s in 2026: How Family Caregivers Can Read the FDA Headline Carefully
- The NIA 2026 Dementia Care and Caregiving Summit Report: Questions Long-Distance Caregivers Can Ask Local Care Programs
