Elecsys® Phospho-Tau (217P) Plasma
One Alzheimer’s biomarker with one set of cutoffs to bridge the gap between primary and specialty care settings
The path to an Alzheimer's diagnosis is often a maze of uncertainty. Roche’s Elecsys® pTau217 is the first single-biomarker, FDA-cleared blood test designed to aid in the identification of Alzheimer's-associated amyloid pathology in patients aged 55 and older presenting with signs, symptoms or complaints of cognitive decline. It features a clinically validated, unified dual-cutoff approach to reliably rule-in and rule-out amyloid pathology across primary and specialty care settings.
By using a test with the same dual cutoffs for both Primary Care Providers (PCPs) and specialists, Elecsys® pTau217 is designed to streamline the diagnostic pathway, enabling early detection, more efficient referrals and more accurate clinical decisions.
Traditional methods for confirming amyloid pathology, such as positron emission tomography (PET) scans and cerebrospinal fluid (CSF) assessments can be expensive, difficult to access, and perceived as more invasive. The Elecsys® pTau217 Plasma assay can streamline this process by providing a minimally invasive, blood-based test to be used in the diagnostic pathway in conjunction with other clinical information.
Intended use
The Elecsys® Phospho-Tau (217P) Plasma assay is an in vitro diagnostic immunoassay for the quantitative determination of the phospho-tau (217P) (pTau217) protein in human plasma from individuals aged 55 years and older.
The assay is intended as an aid in identifying patients with amyloid pathology presenting with signs, symptoms, or complaints of cognitive decline associated with Alzheimer’s disease. The result must be used in the diagnostic pathway in conjunction with other clinical information.
Clinical result interpretation
Results are interpreted based on three distinct zones, an approach shown to improve diagnostic accuracy and to guide patient follow up.
Result classification |
Clinical indication |
Recommended action |
Negative (pT217p ≤ 0.223 pg/mL) |
Low likelihood of amyloid pathology. |
Further clinical investigation into other causes of cognitive decline is recommended. |
Intermediate (0.223 pg/mL < pT217p ≤ 0.378 pg/mL) |
Indeterminate for the presence of amyloid pathology. |
Consider further testing, such as CSF testing or an amyloid PET scan. |
Positive (pT217p > 0.378 pg/mL) |
High likelihood of amyloid pathology. This result, in the absence of clinical evaluation, does not establish a diagnosis of Alzheimer's disease. |
In the appropriate clinical context, detection of amyloid pathology can streamline the path to diagnosis and therapy. |
Operational efficiency
The Elecsys® pTau217 test is fully automated and designed to integrate seamlessly into routine laboratory workflows on existing cobas® e immunoassay analyzers.
Product specification |
Value |
Turnaround time |
18 minutes |
Sample volume |
60 µL |
Sample material |
Human K2-EDTA or K3-EDTA plasma |
Onboard stability |
16 weeks |
Calibration frequency |
Once per reagent lot |
Platform compatibility |
cobas® e 402 and e 801 analyzers |
Clinical performance
Validated in a multicenter prospective study, the Elecsys® pTau217 assay demonstrates high diagnostic accuracy across different disease prevalence settings.
Care setting |
Primary care |
Specialty care |
Sensitivity (PPA)(%) (95% CI) |
96.1% |
94.2% |
| Specificity (NPA) (%) (95% CI) | 94.7% | 93.1% |
Negative Predictive Value (NPV)(%) (95% CI) |
98.6% |
93.7% |
Positive Predictive Value (PPV)(%) (95% CI) |
78.3% |
90.2% |
Clinical performance based on comparison of Elecsys® pTau217 plasma results with PET-CT scan visual reads. Predictive values are heavily influenced by the prevalence of the condition in the tested population. Therefore, results must be interpreted within the context of a comprehensive clinical assessment. Primary care patients with positive results near the upper cutoff may require further diagnostic evaluation or specialist follow-up to confirm or exclude the presence of amyloid pathology.
Ordering information
Material description |
Material number |
Pack size |
pT217p Elecsys E2G 100 (e-pack) |
10285583190 |
100 tests |
pT217p CalSet |
10285656190 |
4 x 1.0 ml |
pT217p PreciControl |
10285664190 | 6 x 1.0 ml |
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References
- Elecsys® Phospho-Tau (217P) Plasma Method Sheet
- Delaby C, Gabelle A, Duchiron M, et al. Impact of preanalytical delay on the performance of plasma Aβ42, Aβ42/40, p-tau217, and p-tau217/Aβ42 in detecting brain amyloidosis in the ALZAN cohort. Alzheimer’s Dement. 2025;21:e70867. https://doi.org/10.1002/alz.70867