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Plavix Sensitivity Genotype (CYP2C19)

Justification

Plavix (clopidogrel) is a commonly prescribed antiplatelet medication for the prevention of arterial thrombosis. A significant subset of patients treated with clopidogrel do not show adequate antiplatelet response due to factors such as variability in drug metabolism, drug interactions, and compliance, leading to increased risk of recurrent cardiovascular events. Plavix is a prodrug that is converted to its active metabolite in the liver by the cytochrome P450 enzyme system. Plavix sensitivity genotyping of CYP2C19 can be used to detect the presence of alleles (CYP2C19*2, CYP2C19*3) that lead to decreased metabolism and reduced conversion of Plavix to its active form (Plavix "resistance"), or alleles (CYP2C19*17) that lead to increased metabolism and conversion of Plavix to its active form.

STAT: < 48 hours (M-F)

RT-PCR

Draw Tube: Purple Top

Sample Type: EDTA Whole Blood

Specimen Requirements

Sample Type Volume Required Minimum Volume Stability
PREFERRED EDTA Whole Blood 3mL 1mL Room Temp.: 1 month
Refrigerated: 1 month
ALTERNATIVE Cheek swab 2 swab - Room Temp.: 1 month
Refrigerated: 1 month
REJECTION CRITERIA Sample contamination; sample compromised
SPECIAL INSTRUCTIONS -

General Information

METHODOLOGY RT-PCR
STAT TAT < 48 hours (M-F)
STAT TAT Performance > 90% of results released in 48 hours
ROUTINE TAT < 1 week
ALTERNATIVE NAMES Plavix genetic test, P2Y12 genetic test
DESCRIPTION This test detects the -806C>T (CYP2C19*17), 17948G>A (CYP2C19*3), and 19154G>A (CYP2C19*2) variants using real-time PCR. It can detect individuals who are homozygous or heterozygous for each of the three variants, or individuals who carry none of the variants (CYP2C19*1/*1 individuals).
LIMITATIONS This test does not detect CYP2C19 genotypes other than *2, *3, or *17. Other genotypes which may influence Plavix metabolism are not detected by this test, and individuals carrying these other genotypes will be identified as CYP2C19*1/*1 (normal metabolism) individuals.
NORMAL RANGE Interpretation
ASSOCIATED TESTING -
REFERENCES -
SAMPLE REPORT Upon request
NEW YORK STATE APPROVED No

Test Codes

ORDER CODE P3051
CPT CODE 81225
LOINC CODE 57132-3