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Test ID WARFC Warfarin Sensitivity Genotype by Sequence Analysis, Saliva

Useful For

Identifying patients who may require warfarin dosing adjustments(2,3) including:

-Patients who have previously been prescribed warfarin and have required multiple dosing adjustments to maintain the international normalized ratio in the target range

-Patients with a history of thrombosis or bleeding when taking warfarin

-Patients being started on a first prescription for warfarin


Genotyping patients who prefer not to have venipuncture done

Genetics Test Information

This test is used for assessing CYP2C9 and VKORC1 genes for polymorphisms affecting the metabolism of warfarin (Coumadin). This assay should be ordered on patients who are receiving warfarin for the first time or who require decreased warfarin dosing to maintain the international normalized ratio (INR) in the therapeutic range.

Method Name

Polymerase Chain Reaction (PCR) Followed by DNA Sequence Analysis

Reporting Name

Warfarin Sensitivity, Saliva

Specimen Type


Specimen Required

Multiple saliva genotype tests can be performed on a single specimen after a single extraction. See Multiple Saliva Genotype Tests in Special Instructions for a list of tests that can be ordered together.


Supplies: DNA Saliva Collection Kit (T651: fees apply)

Specimen Volume: Full tube

Collection Instructions:

1. Fill tube to line.

2. Send specimen in original container per kit instructions.

Specimen Minimum Volume

1 mL

Specimen Stability Information

Specimen Type Temperature Time
Saliva Ambient

Reference Values

An interpretive report will be provided.

Day(s) and Time(s) Performed

Monday, Thursday; 8 a.m.

Performing Laboratory

Mayo Medical Laboratories in Rochester

CPT Code Information

81227-CYP2C9 (cytochrome P450, family 2, subfamily C, polypeptide 9) (eg, drug metabolism), gene analysis, common variants (eg, *2, *3, *5, *6)

81355-VKORC1 (vitamin K epoxide reductase complex, subunit 1) (eg, warfarin metabolism), gene analysis, common variants (eg, -1639/3673)

LOINC Code Information

Result ID Test Result Name Result LOINC Value
36458 Warfarin Sensitivity In Process
36459 CYP2C9 Star Alleles In Process
36460 VKORC1 -1639 Result In Process
36461 Warfarin Sensitivity Interpretation 69047-9
36462 Reviewed by No LOINC Needed

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.


New York Clients-Informed consent is required. Please document on the request form or electronic order that a copy is on file. An Informed Consent for Genetic Testing (Supply T576) is available in Special Instructions.