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Beaumont Laboratory

Warfarin Sensitivity Genotyping

CYP2C9/VKORC1 Genotype for Coumadin Hyper-Responsiveness, CYP2C9/VKORC1 Genotype for Warfarin Hyper-Responsiveness, EPIC: LAB7043, SOFT: XYP29

Specimen Collection Criteria

Collect: One 10 mL whole blood in Lavender-top EDTA tube. (Min: 1.0 mL)

Physician Office/Drawsite Specimen Preparation

Do not centrifuge. Maintain whole blood refrigerated (2-8°C or 36-46°F) prior to transport.

Preparation for Courier Transport

Transport: Whole blood refrigerated (2-8°C or 36-46°F). (Min: 1.0 mL whole blood)

Rejection Criteria

  • Specimen not collected as indicated.
  • This test will only be performed once in a lifetime for a patient.


Specimen Stability for Testing:

Whole Blood
Room Temperature (20-26°C or 68-78.8°F): 72 hours
Refrigerated (2-8°C or 36-46°F): 2 weeks
Frozen (-20°C/-4°F or below): 1 month

Specimen Storage in Department Prior to Disposal:

Refrigerated (2-8°C or 36-46°F): 7 days

Extracted DNA may be available for additional testing if clinically indicated. Contact the Molecular Pathology Laboratory for verification.


Sent to ARUP Laboratories, Salt Lake City, UT.


Monday, Thursday.
Results available in 6-11 days.

Reference Range

By report.

Test Methodology

PCR (Polymerase Chain Reaction)/Fluorescence Monitoring.


This test detects the wild type alleles fo the CYP2C9 and VKORC1 genes and the mutant alleles *2 and *3 of CYP2C9 and VKORC1 mutation -1639G>A.

Clinical Utility

  • The CYP2C9 enzyme metabolizes warfarin and the Vitamin K Epoxide Reductase Complex subunit 1 (VKORC1) is the target of warfarin therapy. The combined CYP2C9/VKORC1 genotype can be used to predict a patient's response to warfarin therapy and individualize warfarin dose.
  • Testing is recommended on patients to be started on Warfarin in order to individualize the initial dose, and also on patients who have not been tested before initiation of therapy, to adjust maintenance dose.

CPT Code

81227, 81355.

Test Codes


Last Updated


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This directory currently reflects information only for specimens collected and/or processed at the Farmington Hills, Grosse Pointe, Royal Oak, and Troy campuses.