CPT 0030U, G9143 - Genotype-Guided Warfarin Dosing

Code Description CPT

0030U Drug metabolism (warfarin drug response), targeted sequence analysis (ie, CYP2C9, CYP4F2, VKORC1, rs12777823) (new code effective 1/1/18)


G9143 Warfarin responsiveness testing by genetic technique using any method, any number of specimen(s)


Genotype-Guided Warfarin Dosing


Introduction
Warfarin (Coumadin) is a blood thinner that works by reducing the blood’s ability to clot. It’s often prescribed to prevent blood clot formation in people who have conditions like atrial fibrillation. Finding the correct dose can be complicated. Too high a dose can cause bleeding. Too low a dose can result in blood clots being formed. Factors such as age, weight, use of other medications, and smoking go into the calculation of how much is prescribed. Once the drug is prescribed, the doctor then adjusts the dose based on blood tests. Two genes have been associated with how well the body processes warfarin. Genetic tests have been developed to look at these genes to try to determine warfarin dosing. These genetic tests are investigational (unproven). Medical studies do not show whether genetic testing to try to adjust warfarin doses leads to better health results. More studies are needed.

Note:   The Introduction section is for your general knowledge and is not to be taken as policy coverage criteria. The rest of the policy uses specific words and concepts familiar to medical professionals. It is intended for providers. A provider can be a person, such as a doctor, nurse, psychologist, or dentist. A provider also can be a place where medical care is given, like a hospital, clinic, or lab. This policy informs them about when a service may be covered.

Test Investigational 

Testing of cytochrome p450 2C9 (CYP2C9), P450 4F2 (CYP4F2), and vitamin K epoxide reductase subunit C1 (VKORC1)

Coding Genotyping for CYP2C9, CYP4F2, and VKORC1 variants is considered investigational to manage the administration and dosing of warfarin, including: * Guiding the initial  warfarin dose  * Decreasing the time needed to achieve a stable international  normalized ratio (INR) * Reducing the risk of serious bleeding

Related Information 

Genetics Nomenclature Update
The Human Genome Variation Society nomenclature is used to report information on variants found in DNA and serves as an international standard in DNA diagnostics (see  Table 1). The Society’s nomenclature is recommended by the Human Variome Project, the HUman Genome Organization, and by the Human Genome Variation Society itself.  The American College of Medical Genetics and Genomics and the Association for Molecular Pathology standards and guidelines for interpretation of sequence variants  represent expert opinion from both organizations, in addition to the College of American Pathologists. These  recommendations primarily apply to genetic tests used in clinical laboratories, including genotyping, single genes, panels, exomes, and genomes. Table 2 shows the  recommended standard terminology*“pathogenic,” “likely pathogenic,” “uncertain significance,” “likely benign,” and “benign”*to describe variants identified that cause  Mendelian disorders.

Table 1. Nomenclature to Report on Variants Found in DNA
Previous  Updated  Definition

Mutation Disease-associated variant

Disease-associated change in the DNA sequence
Variant Change in the DNA sequence 
Familial variant Disease-associated variant identified in a proband for use in subsequent targeted genetic testing in first-degree relatives
Table 2. ACMG-AMP Standards and Guidelines for Variant Classification
Variant Classification Definition
Pathogenic Disease-causing change in the DNA sequence
Likely pathogenic Likely disease-causing change in the DNA sequence 
Variant of uncertain significance Change in DNA sequence with uncertain effects on disease
Likely benign Likely benign change in the DNA sequence
Benign Benign change in the DNA sequence
ACMG: American College of Medical Genetics and Genomics; AMP: Association for Molecular Pathology.

Genetic Counseling

Experts recommend formal genetic counseling for patients who are at risk for inherited disorders and who wish to undergo genetic testing. Interpreting the results of genetic tests and understanding risk factors can be difficult for some patients; genetic counseling helps individuals understand the impact of genetic testing, including the possible effects the test results could have on the individual or their family members. It should be noted that genetic counseling may alter the utilization of genetic testing substantially and may reduce inappropriate testing; further, genetic counseling should be performed by an individual with experience and expertise in genetic medicine and genetic testing methods.