Test Details
Clopidogrel Response (CYP2C19) Genotype Test
CYP2C19 polymorphisms are inherited variations in the DNA sequence of the gene that codes for the cytochrome P450 (CYP) enzyme 2C19. This enzyme is found in the liver and converts the pro-drug clopidogrel (PLAVIX®) to its active form.
Knowing CYP2C19 genotype is important prior to angioplasty to assure proper treatment with clopidogrel or prasugrel to prevent the complications of either stent closure or significant bleeding. The intended use of CYP2C19 testing is as an aid in treatment decisions related to dosage of clopidogrel (Plavix). The genetic test identifies individuals that have reduced metabolism of clopidogrel, thus requiring higher amounts of the drug in order to reach an efficacious dose of the active agent, or sometimes require a different agent such as prasurgrel or ticagrelor, because they do not metabolize clopidogrel to its active form at all. Moreover there is another group of patients identified by this testing who has increased metabolism of clopidogrel to its active form, and such patients require a decreased dose of clopidogrel to prevent bleeding complications.
Methodology
Real time polymerase chain reaction (PCR)
Patient Preparation
None
Preferred Specimen
1.0 mL whole blood collected in EDTA (Lavender Top)
Alternate Specimen
- Buccal swab
- Dried Blood collected on an AdvanceDx 100 card
Transport Temperature
Refrigerated (ship on frozen cold packs)
Stability
Refrigerated: 15 days
Lab Values
Clopidogrel Response (CYP2C19) Genotype Test
- Normal Clopidogrel Metabolizers
- Genotype *1/*1
- Genotype *2/*17 (metabolism is not known but is assumed to fall in the normal category)
- Genotype *3/*17 (metabolism is not known but is assumed to fall in the normal category)
- Increased Clopidogrel Metabolizer
- Genotype *1/*17
- Decreased Clopidogrel Metabolizers
- Genotype *1/*2
- Genotype *1/*3
- Markedly Increased Clopidogrel Metabolizer
- Genotype *17/*17
- Markedly Decreased Clopidogrel Metabolizers
- Genotype *17/*17
- Genotype *2/*2
- Genotype *3/*3
- Genotype *2/*3
*2/*17, *3/*17 metabolism is not known but is assumed to fall in the normal category
Clinical Significance
Clopidogrel Response (CYP2C19) Genotype Test
See lab values section above.
Treatment Options
Clopidogrel Response (CYP2C19) Genotype Test
- Normal Clopidogrel Metabolizers (genotypes *1/*1, *2/*17, *3/*17)
- Normal doses of clopidogrel can be used
- Increased Clopidogrel Metabolizer (genotype *1/*17)
- Only normal doses of clopidogrel, if indicated, are recommended
- Decreased Clopidogrel Metabolizers (genotypes *1/*2, *1/*3)
- The clopidogrel dose, if indicated, may need to be increased
- Markedly Increased Clopidogrel Metabolizer (genotype *17/*17)
- Only normal doses or lower than normal doses of clopidogrel are recommended, if indicated
- Markedly Decreased Clopidogrel Metabolizers (genotypes *2/*2, *3/*3, *2/*3)
- Another agent such as ticagrelor or prasugrel, if indicated, is recommended
