nAbCyte™ Anti‑AAVRh74var HB‑FE Assay (nAbCyte Assay)
Companion Diagnostic
nAbCyte™ Anti‑AAVRh74var HB‑FE Assay (nAbCyte Assay) is an FDA-approved companion diagnostic used to help identify patients who may be eligible for targeted therapies.
Use
The nAbCyte™ Anti‑AAVRh74var HB‑FE Assay is a qualitative in vitro companion diagnostic device used to detect neutralizing antibodies against the AAVRh74var capsid in serum from patients diagnosed with moderate to severe hemophilia B, in order to determine eligibility for Pfizer’s gene therapy BEQVEZ™ (fidanacogene elaparvovec). Patients testing positive are considered ineligible for BEQVEZ, while those testing negative may proceed with treatment. Intended for use in serum from adult patients previously diagnosed with hemophilia B. ([labcorp.com](https://www.labcorp.com/content/labcorp/us/en/test-menu/sponsored-testing/pfizer/ca-en/nabcytehemb.html?utm_source=openai))
Special Instructions
Healthcare providers must register once for program participation, complete and use the nAbCyte‑specific Test Request Form provided in the Welcome Package, receive collection and shipping instructions, then order via that form. Program was available only in Canada as of 5 months ago; in the U.S., the testing program is no longer available in the United States as of May 2025. Contact [email protected] for questions. ([labcorp.com](https://www.labcorp.com/content/labcorp/us/en/test-menu/sponsored-testing/pfizer/ca-en/nabcytehemb.html?utm_source=openai))
Limitations
Not provided.
FDA ApprovedCompanion Diagnostic
Methodology
Other
Biomarkers
AAVRh74var neutralizing antibodies
Protein
Result Turnaround Time
7-10 days
Related Documents
For more information, please review the documents below
Specimen
Serum
Volume
1 mL preferred; 0.2 mL minimum
Minimum Volume
0.2 mL
Container
Red‑top tube (glass or plastic clot activator, silicon‑coated plastic); submission in screw‑cap polypropylene transport tube
Collection Instructions
Collect in red‑top tube (no gel barrier); invert to mix; allow to clot ≥30 minutes or until complete; centrifuge at 1,500‑2,000 g for 15 minutes; transfer serum within 6 hours into screw‑cap polypropylene tube
Storage Instructions
Freeze serum at ‑20 °C in a non‑defrosting freezer; do not flash‑freeze on dry ice; do not thaw after freezing
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 20 hours |
| Refrigerated | 3 days at 4 °C |
| Frozen | 1 month at ‑20 °C |
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