Clopidogrel CYP2C19 Genotyping

CPT: 81225
Updated on 8/9/2019
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Expected Turnaround Time

6 - 10 days


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Specimen Requirements


Specimen

Whole blood or LabCorp buccal swab kit (Buccal swab collection kit contains instructions for use of a buccal swab, PeopleSoft N° 3177.)


Volume

7 mL whole blood or LabCorp buccal swab kit


Minimum Volume

3 mL whole blood or two buccal swabs


Container

Lavender-top (EDTA) tube, yellow-top (ACD) tube, or LabCorp buccal swab kit


Storage Instructions

Maintain specimen at room temperature or refrigerate at 4°C.


Causes for Rejection

Frozen or hemolyzed specimen; quantity not sufficient for analysis; one buccal swab; improper container; wet buccal swab


Test Details


Use

Clopidogrel is a prodrug that is metabolized to its active component by several cytochrome P450 proteins of which CYP2C19 plays a key role. Among clopidogrel treated patients, intermediate (IM) or poor (PM) metabolizers are associated with reduced platelet inhibition and an increased risk of cardiovascular complications, such as myocardial infarction, stroke, stent thrombosis, and/or death, as compared with normal (extensive) metabolizers. Intermediate to normal metabolizers (IM-EM) are anticipated to have a range of reduced to normal enzyme activity. Normal metabolizers (EM) are anticipated to have normal enzyme activity. Individuals who are carriers of the *17 allele are ultrarapid metabolizers (UM) and may have an enhanced response to clopidogrel. Ultrarapid metabolizers may be at increased risk of bleeding. Other common drugs metabolized by the 2C19 pathway include proton pump inhibitors (omeprazole), anticonvulsants (phenytoin and diazepam), and tricyclic antidepressants (amitriptyline and nortriptyline).


Limitations

This assay does not detect other variants in the CYP2C19 gene that may affect metabolic activity.

The metabolism of drugs is also influenced by ethnicity, diet, and other medications. All factors should be considered prior to initiating new therapy. This testing does not rule out the possibility of variant alleles in other drug metabolism pathways.


Methodology

DNA analysis of the Cytochrome P450 2C19 gene (OMIM 124020, 10q24.1-10q24.3) is performed using primer extension chemistry. Multiplex PCR amplifies DNA fragments containing the variants below. Primer extension then generates a biotin-labeled product to perform flow-sorted detection of both normal and variant sequences. Molecular-based testing is highly accurate, but as in any laboratory test, rare diagnostic errors may occur.

Alleles detected: *1,*2,*3,*17

*1 represents detection of the normal sequence for the variant sites tested.


References

Scott SA, Sangkuhl K, Stein CM, et al. Clinical Pharmacogenetics Implementation Consortium guidelines for CYP2C19 genotype and clopidogrel therapy: 2013 Update. Clin Pharmacol Ther. 2013 Sep;94(3):317-323.23698643
Sibbing D, Koch W, Gebhard D, et al. Cytochrome 2C19*17 allelic variant, platelet aggregation, bleeding events, and stent thrombosis in clopidogrel-treated patients with coronary stent placement. Circulation. 2010 Feb 2;121(4):512-518.20083681
Simon T, Verstuyft C, Mary-Krause M, et al. Genetic determinants of response to clopidogrel and cardiovascular events. N Engl J Med. 2009 Jan 22;360(4):363-75.19106083

LOINC® Map

Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
511710 Clopidogrel P450 2C19 504204 2C19 Genotype: 57132-3
511710 Clopidogrel P450 2C19 504205 2C19 Metabolic Activity: 79714-2
511710 Clopidogrel P450 2C19 504632 Director Review: 69426-5
511710 Clopidogrel P450 2C19 504379 Interpretation: 72879-0
511710 Clopidogrel P450 2C19 504380 CYP2C19 Information: 49549-9
511710 Clopidogrel P450 2C19 000000 MGRM Informed Consent Review N/A

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The LOINC® codes are copyright © 1994-2018, Regenstrief Institute, Inc. and the Logical Observation Identifiers Names and Codes (LOINC) Committee. Permission is granted in perpetuity, without payment of license fees or royalties, to use, copy, or distribute the LOINC® codes for any commercial or non-commercial purpose, subject to the terms under the license agreement found at https://loinc.org/license/. Additional information regarding LOINC® codes can be found at LOINC.org, including the LOINC Manual, which can be downloaded at LOINC.org/downloads/files/LOINCManual.pdf