Emicizumab, Modified One Stage Assay Factor VIII, Plasma
Use
This assay is useful for monitoring compliance with emicizumab (Hemlibra) therapy or the potential development of antidrug antibodies. It is not indicated for monitoring factor VIII infusions or diagnosing hemophilia. Emicizumab functions as a bispecific antibody that bridges factor IXa and factor X to mimic factor VIII activity. In clinical trials, outcomes were achieved without measuring plasma emicizumab levels, but measurement may be useful in select scenarios such as breakthrough bleeding or suspected noncompliance or antidrug antibody formation.
Special Instructions
Order F8A / Coagulation Factor VIII Activity Assay, Plasma for monitoring factor VIII infusions or diagnosing hemophilia. If specimen is priority, mark request form, provide reason, and request a call-back. For ordering, complete and send Coagulation Test Request (T753) with specimen. The test uses a modified one‑stage optical clot‑based assay.
Limitations
Endogenous or exogenous factor VIII above approximately 10% by bovine chromogenic FVIII assay may lead to falsely elevated emicizumab levels. Excess heparin or dilution contamination from collection via intravenous access may artifactually decrease results. Use polypropylene aliquot tubes to prevent activation artifacts. Double‑centrifuged specimens are critical to avoid spurious results from platelet contamination.
New York Approved
Methodology
Other (Optical Clot-Based)
Biomarkers
LOINC Codes
- 99614-0
- 99614-0
Result Turnaround Time
1-7 days
Related Documents
For more information, please review the documents below
Specimen
Plasma
Volume
1 mL
Minimum Volume
0.5 mL
Container
Light‑blue top (3.2% sodium citrate) tube; Sarstedt Aliquot Tube, 5 mL (T914); plastic vial (polypropylene preferred)
Collection Instructions
Draw platelet‑poor plasma. Centrifuge, transfer plasma to plastic vial, centrifuge again, aliquot leaving 0.25 mL in bottom tube. Freeze plasma immediately (within 4 hours) at −20 °C or ideally −40 °C or below.
Patient Preparation
Patient should not receive factor VIII infusions for at least 12 to 24 hours prior to collection.
Causes for Rejection
Specimens evaluated for suitability; platelet contamination may cause inaccurate results.
Stability Requirements
| Temperature | Period |
|---|---|
| Frozen | 42 days |