PrecivityAD2™ (C2N Diagnostics)

PrecivityAD2™ is a blood test developed by C2N Diagnostics that measures two Alzheimer's biomarkers — the amyloid beta 42/40 ratio (Aβ42/40) and the ratio of phosphorylated to non-phosphorylated tau-217 (p-tau217/np-tau217) — and combines them into a single score called the Amyloid Probability Score 2 (APS2). Codex Genetics is the exclusive distributor of PrecivityAD2™ in Hong Kong. The test enables neurologists to determine whether a patient's brain has amyloid plaques — the hallmark of Alzheimer's disease — from a simple blood draw, as an alternative to an amyloid PET brain scan.

Adults aged ≥50 with signs or symptoms of mild cognitive impairment (MCI) or dementia who are being evaluated for Alzheimer's disease. Clinicians deciding on anti-amyloid therapy (lecanemab, donanemab) who require biomarker confirmation. Specialist memory and neurology clinics requiring high-accuracy biomarker-confirmed AD diagnosis.

Use EDTA vacuum blood collection tubes (purple cap) to draw 10 mL of venous blood.

Transfer to 4°C for immediate storage and arrange shipment to Codex Genetics Laboratory (within 2 hours)

Available exclusively through Codex Genetics in Hong Kong. A healthcare professional prescription is required. Please contact Codex Genetics for test requisition forms, sample collection kits, cold-chain shipping instructions, and result delivery.

Amyloid Probability Score 2 (APS2) reported on 0–100 scale: Positive ≥48 Negative ≤48 Individual Aβ42/40 ratio and % of p-Tau217 ratio also reported.

A positive APS2 (≥48) is consistent with a positive amyloid PET scan; it reflects a high likelihood of brain amyloid plaques and is therefore consistent with a neuropathological diagnosis of Alzheimer’s disease. A negative APS2(0-47) is consistent with a negative amyloid PET scan; it reflets a low likelihood of brain amyloid plaques and is therefore not consistent with a neuropathological diagnosis of Alzheimer’s disease(AD). The APS2 result should be interpreted in conjunction with other patient information. Clinical correlation is recommended.

PrecivityAD2™ measures two NIA-AA 2024 Core Tier 1 biomarkers in a single mass spectrometry assay. Published data from C2N Diagnostics (Alzheimer's & Dementia 2023) show 91.0% concordance with amyloid PET (AUC 0.92). The Aβ42/40 ratio reflects amyloid plaque burden; the p-tau217/np-tau217 ratio (the pT217 ratio) reflects tau phosphorylation driven by amyloid plaques. The combined APS2 score significantly outperforms either biomarker alone. The APS2 is reported on a 0–100 scale (positive: ≥48, negative: ≤48). The test uses proprietary immunoprecipitation/liquid chromatography-mass spectrometry (IP/LC-MS/MS) — the same gold-standard platform validated in the Mayo Clinic PrecivityAD test. Per NIA-AA 2024 revised criteria (Jack CR Jr et al., Alzheimer's & Dementia 2024; DOI: 10.1002/alz.13859), both Aβ42/40 and p-tau217 are Core Tier 1 AD biomarkers.