Lab Test

Warfarin Sensitivity Genotyping

CYP2C9/VKORC1 Genotype for Coumadin Hyper-Responsiveness, CYP2C9/VKORC1 Genotype for Warfarin Hyper-Responsiveness

Test Codes

EPIC: LAB7043, Beaker: XYP29, ARUP: 3001541


Send Outs

Specimen Collection Criteria

Collect: One 4 mL whole blood in Lavender-top EDTA tube. (Minimum: 1.0 mL)

This test will only be performed once in a lifetime for a patient.

Physician Office/Draw 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). (Minimum: 1.0 mL whole blood)

Rejection Criteria

  • Specimen not collected as indicated.
  • Plasma or Serum
  • Sodium heparin tube
  • Lithium heparin


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): 1 week
Frozen (-20°C/-4°F or below): 1 month


Sent to ARUP Laboratories, Salt Lake City, UT.


Results available in 6-11 days.

Reference Range

By report.

Test Methodology

PCR (Polymerase Chain Reaction)/Fluorescence Monitoring.


By report.

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 Codes

81227, 81355.
LOINC:  31208-2, 50722-8


Last Updated


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