CYP2C19 Genotype (Cytochrome p450 2C19) for Drug Metabolism

Methodology: 
Real-time polymerase chain reaction-based/fluorescence-monitoring test
Performed: 
Monday - Friday
Reported: 
1 - 2 days
Use: 

This test identifies the CYP2C19 genotype to determine the patient's rate of metabolism for drugs activated or inactivated by this pathway. It has particular importance in metabolizing the drug clopidogrel (Plavix®).

Specimen Requirements: 
Collect at least 3 mL of blood in:
  • EDTA: Lavender-top tube;
  • K2EDTA: Pink-top tube; or
  • ACD Solution A or B: Yellow-top tube. 

Severely hemolyzed, clotted and/or frozen blood specimens, and specimens in heparin (green-top) tubes are not accepted.

Specimen Preparation: Transport 3 mL of whole blood. (minimum 1 mL)

Storage/Transport Temperature: Refrigerated

Stability (collection to initiation of testing):
  • Ambient: 72 hours
  • Refrigerated: 1 week
  • Frozen: Unacceptable
Reference Values: 

No allelic variants detected (*1/*1)

Interpretation Data: 

Analytical Interpretation: The report includes the patient's diplotype of CYP2C19 genes and is reported using star alleles as follows:

  • *1/*1 for no allelic variant present; or
  • *17/*17 for a homozygous c.991A>G genotype (which has increased function).
CYP2C19 Allelic Variants Tested
Allele Nucleotide Effect Predicted Enzyme Activity
*1 No allelic variant Normal Normal
*2 c.681G>A Splicing defect Non-functional
*3 c.636G>A New stop codon Non-functional
*4 c.1A>G Loss of initiation Non-functional
*5 c.1297C>T R433W Non-functional
*6 c.395G>A R132Q Non-functional
*8 c.358T>C W120R Non-functional
*10 c.680C>T P227L Decreased function
*17 c.991A>G Increased transcription Increased function

Clinical Interpretation: The clinical significance of the result along with recommendations for therapy will be provided.
  • Normal metabolism
  • Impaired metabolism
  • Very imparied metabolism
  • Enhanced metabolism
  • Unknown effect on metabolism
  • Indeterminate result
CPT Code (s): 

81225

Notes: 

UFHPL Test #: 10070

Test Directory