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HelpTest Code EMICZ Emicizumab, Modified One Stage Assay Factor VIII, Plasma
Ordering Guidance
Necessary Information
If priority specimen, mark request form, give reason, and request a call-back.
Specimen Required
Specimen Type: Platelet-poor plasma
Patient Preparation: For at least 12 to 24 hours before specimen collection, the patient should not be given infusions of factor VIII concentrates.
Supplies: Sarstedt Aliquot Tube, 5 mL (T914)
Collection Container/Tube: Light-blue top (3.2% sodium citrate)
Submission Container/Tube: Plastic vial (polypropylene preferred)
Specimen Volume: 1 mL
Collection Instructions:
1. For complete instructions, see Coagulation Guidelines for Specimen Handling and Processing
2. Centrifuge, transfer all plasma into a plastic vial, and centrifuge plasma again.
3. Aliquot plasma into a plastic vial, leaving 0.25 mL in the bottom of centrifuged vial.
4. Freeze plasma immediately (no longer than 4 hours after collection) at -20° C or, ideally, at -40° C or below.
Additional Information:
1. Double-centrifuged specimen is critical for accurate results as platelet contamination may cause spurious results.
2. Each coagulation assay requested should have its own vial.
Useful For
Monitoring compliance or potential development of an antidrug antibody
This assay is not indicated for monitoring factor VIII infusions or for making a diagnosis of hemophilia.
Disease States
- Hemophilia A
Special Instructions
Method Name
Optical Clot-Based
Reporting Name
Emicizumab, modified OSA FVIII, PSpecimen Type
Plasma Na CitSpecimen Minimum Volume
0.5 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Plasma Na Cit | Frozen | 42 days |
Clinical Information
Emicizumab (Hemlibra) is a bispecific antibody directed toward factor IXa and factor X, bridging in close enough proximity to mimic and replace factor VIII. Emicizumab has been approved by the US Food and Drug Administration for prevention of bleeding in hemophilia A patients, both with and without inhibitors to factor VIII.
In clinical trials, clinical outcomes were achieved without the measurement of plasma emicizumab levels to inform and make management decisions. However, in selected clinical situations, measurement of drug level would be useful. (eg, for patients experiencing break through bleeding episodes, if levels are not detectable or below the published [observed] ranges, this may imply noncompliance or development of an antidrug antibody.)
Reference Values
<1 mcg/mL
Interpretation
Therapeutic ranges for plasma emicizumab concentrations have not been established. Trough plasma concentrations observed during clinical trials ranged between 35 and 55 micrograms/mL.
Cautions
The presence of endogenous and exogenous factor VIII (approximately > 10% [>0.1 IU/mL] by bovine chromogenic FVIII assay) will cause the emicizumab level to be falsely elevated.
Excess heparin and dilution contamination due to improper specimen collection through an intravenous access device may result in artifactually decreased results.
Aliquot tubes should be made with non-activating material, such as polypropylene (Aliquot Tube, 5 mL [T465]).
Method Description
The emicizumab (Hemlibra) assay is a modification to the one stage factor VIII assay performed on the Instrumentation Laboratory (IL) ACL TOP using the activated partial thromboplastin time (IL SynthASil APTT) method and a factor-deficient substrate. Patient plasma is combined and incubated with a factor VIII-deficient substrate (Precision Biologic, normal plasma depleted of factor VIII by immunoadsorption) and an APTT reagent. After a specified incubation time, calcium is added to trigger the coagulation process in the mixture. Then the time to clot formation is measured optically at a wavelength of 671 nm and interpolated against a drug specific calibration.(Owen CA Jr, Bowie EJW, Thompson JH Jr. Diagnosis of bleeding disorders. 2nd ed. Little, Brown and Company; 1975; Cielsa B. Defects of plasma clotting factors. In: Hematology in Practice. 3rd ed. FA Davis; 2019:chap 17)
Performing Laboratory
Mayo Clinic Laboratories in Rochester
Test Classification
This test has been modified from the manufacturer's instructions. Its performance characteristics were determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.CPT Code Information
80299
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| EMICZ | Emicizumab, modified OSA FVIII, P | 99614-0 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| EMICZ | Emicizumab, modified OSA FVIII, P | 99614-0 |
Day(s) Performed
Monday through Friday