Test Catalog

Test Id : EMICZ

Emicizumab, Modified One Stage Assay Factor VIII, Plasma

Useful For
Suggests clinical disorders or settings where the test may be helpful

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.

Special Instructions
Library of PDFs including pertinent information and forms related to the test

Method Name
A short description of the method used to perform the test

Optical Clot-Based

NY State Available
Indicates the status of NY State approval and if the test is orderable for NY State clients.


Reporting Name
Lists a shorter or abbreviated version of the Published Name for a test

Emicizumab, modified OSA FVIII, P

Lists additional common names for a test, as an aid in searching




Specimen Type
Describes the specimen type validated for testing

Plasma Na Cit

Ordering Guidance

Necessary Information

If priority specimen, mark request form, give reason, and request a call-back.

Specimen Required
Defines the optimal specimen required to perform the test and the preferred volume to complete testing

Patient Preparation: It is preferred that the patient avoid infusions of factor VIII concentrates for at least 12 to 24 hours preceding sample collection for this assay.

Supplies: Sarstedt 5 mL Aliquot Tube (T914)

Specimen Type: Platelet-poor plasma

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 degrees C or, ideally, < or =-40 degrees C.

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.

Special Instructions
Library of PDFs including pertinent information and forms related to the test

Specimen Minimum Volume
Defines the amount of sample necessary to provide a clinically relevant result as determined by the Testing Laboratory

0.5 mL

Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected

Specimen Stability Information
Provides a description of the temperatures required to transport a specimen to the performing laboratory, alternate acceptable temperatures are also included

Specimen Type Temperature Time Special Container
Plasma Na Cit Frozen 42 days

Useful For
Suggests clinical disorders or settings where the test may be helpful

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.

Clinical Information
Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Emicizumab (Hemlibra) is a bi-specific 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 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
Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

<1 mcg/mL

Provides information to assist in interpretation of the test results

Therapeutic ranges for plasma emicizumab concentrations have not been established. Trough plasma concentrations observed during clinical trials ranged between 35 and 55 micrograms/mL.

Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

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 nonactivating material, such as polypropylene (Aliquot Tube, 5 mL [T465]).

Clinical Reference
Recommendations for in-depth reading of a clinical nature

1. Knight T, Callaghan MU: The role of emicizumab, a bispecific factor IXa- and factor X-directed antibody, for the prevention of bleeding episodes in patients with hemophilia A. Ther Adv Hematol. 2018; 9:319-334. doi: 10.1177/2040620718799997

2. Jenkins PV, Bowyer A, Burgess C, et al: Laboratory coagulation tests and emicizumab treatment A United Kingdom Haemophilia Centre Doctors' Organisation guideline. Haemophilia. 2020;26:151-155. doi: 10.1111/hae.13903

3. Jonsson F, Schmitt C, Petry C, Mercier F, Frey N, Retout S: Exposure-response Modeling of Emicizumab for the Prophylaxis of Bleeding in Hemophilia A Patients with and without Inhibitors against Factor VIII. Poster PB0325 presented at: The XXVII Congress of the International Society on Thrombosis and Haemostasis. July 6-10, 2019; Melbourne, Australia

4. Pipie SW, Shima M, Lehle M, et al: Efficacy, safety and pharmacokinetics emicizumab prophylaxis given every 4 weeks in people with haemophilia (HAVEN 4): a multicenter, open-label, non-randomized phase 3 study. Lancet Haematol. 2019;6(6):e295-e305. doi: 10.1016/S2352-3026(19)30054-7

Special Instructions
Library of PDFs including pertinent information and forms related to the test

Method Description
Describes how the test is performed and provides a method-specific reference

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; Meijer P, Verbruggen, Spannagi M: Clotting factors and inhibitors: Assays and interpretation. In: Kottke-Marchant K, ed. Laboratory Hematology Practice. Wiley Blackwell Publishing; 2012:435-446)

PDF Report
Indicates whether the report includes an additional document with charts, images or other enriched information


Day(s) Performed
Outlines the days the test is performed. This field reflects the day that the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time before the test is performed. Some tests are listed as continuously performed, which means that assays are performed multiple times during the day.

Monday through Friday

Report Available
The interval of time (receipt of sample at Mayo Clinic Laboratories to results available) taking into account standard setup days and weekends. The first day is the time that it typically takes for a result to be available. The last day is the time it might take, accounting for any necessary repeated testing.

1 to 7 days

Specimen Retention Time
Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded

7 days

Performing Laboratory Location
Indicates the location of the laboratory that performs the test


Several factors determine the fee charged to perform a test. Contact your U.S. or International Regional Manager for information about establishing a fee schedule or to learn more about resources to optimize test selection.

  • Authorized users can sign in to Test Prices for detailed fee information.
  • Clients without access to Test Prices can contact Customer Service 24 hours a day, seven days a week.
  • Prospective clients should contact their account representative. For assistance, contact Customer Service.

Test Classification
Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR) product.

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
Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Clinic Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.

CPT codes are provided by the performing laboratory.


LOINC® Information
Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the order and results codes of this test. LOINC values are provided by the performing laboratory.

Test Id Test Order Name Order LOINC Value
EMICZ Emicizumab, modified OSA FVIII, P 99614-0
Result Id Test Result Name Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
EMICZ Emicizumab, modified OSA FVIII, P 99614-0

Test Setup Resources

Setup Files
Test setup information contains test file definition details to support order and result interfacing between Mayo Clinic Laboratories and your Laboratory Information System.

Excel | Pdf

Sample Reports
Normal and Abnormal sample reports are provided as references for report appearance.

Normal Reports | Abnormal Reports

SI Sample Reports
International System (SI) of Unit reports are provided for a limited number of tests. These reports are intended for international account use and are only available through MayoLINK accounts that have been defined to receive them.

SI Normal Reports | SI Abnormal Reports