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|Utilization Guidelines||At this time CYP2C19 genotyping is only indicated for patients receiving Plavix (clopidogrel).|
|In House Availability||Monday-Friday day shift only|
|Container type||Lavender top|
|Amount to Collect||3 mL blood|
|Sample type||EDTA Whole blood|
|Preferred volume||3 mL|
|Min. Volume||1 mL|
|UCSF Rejection Criteria||Insufficient sample volume.|
|Processing notes||Call Andrew Smith at 206-4227 when test requests are received. Refrigerate sample and forward to China Basin.|
|Ref Lab Rejection Criteria||Serum, citrated or heparinized plasma received. Samples > 7 days old when received.|
|Normal range||Wildtype 2C19 (*1/*1)|
|Synonyms||Cytochrome P450 2C19|
|Turn around times||1-3 days|
|Additional information|| Note the minimum amount of DNA to perform this assay is 25 ng/mL. samples providing less than this amount will not be tested.
The assay is not validated and cannot be performed on sputum, saliva or buccal swabs.
CYP 2C19 is a liver enzyme that metabolizes many different therapeutic drugs. The gene that codes for CYP 2C19 has significant genetic variances that affect the rate of enzyme activity . The wildtype is defined as the *1/*1 genotype and are "rapid metabolizers." The 2C19 *2 and *3 alleles are associated with reduced hepatic metabolism. Individuals who are heterozygous for 2C19 (*1/*2 or *1/*3) are "intermediate metabolizers" and those who are homozygous (*2/*2, *2/*3. or *3/*3) are "poor metabolizers." The *17 polymorphism is associated with increased hepatic metabolism. These individuals are "ultra-rapid metabolizer."
Genotyping is important for the efficacy of certain drugs particularly clopidogrel (Plavix), a prodrug that requires CYP 2C19 metabolism for activation. Poor and intermediate metabolizers on the standard Plavix dose have a higher rate of adverse cardiac events due to a reduced blood level of the active metabolite. A consideration should be made in these patients to either increase the dosage or to use an alternative oral anti-platelet drug, e.g., prasugrel. Ultra-rapid metabolizers have higher concentrations of the active drug and may be at higher risk for bleeding. Lower doses may be appropriate while maintaining therapeutic efficacy.
The following information outlines the relationship between the polymorphisms detected in the assay and the effect on the enzyme activity encoded by that allele:
|CPT coding||83891, 83900, 83901x4, 83914x20, 83912|
|Last Updated||4/16/2012 10:41:22 AM|
If you have additional questions regarding this test, please call: 415-353-1667