Cytochrome P450 2C19 (CYP2C19) 9 Variants
0051104
Ordering Recommendation
May aid in dose planning for clopidogrel and other drugs metabolized by CYP2C19.
Mnemonic
CYP2C19
Methodology
Polymerase Chain Reaction/Primer Extension
Performed
Mon, Thu
Reported
7-14 days  
New York DOH Approval Status
This test is New York DOH approved.
Submit With Order
Specimen Required
Patient Preparation
  
Collect
Lavender (EDTA), pink (K2EDTA), or yellow (ACD Solution A or B).  
Specimen Preparation
Transport 3 mL whole blood. (Min: 1 mL)  
Storage/Transport Temperature
Refrigerated.  
Unacceptable Conditions
  
Remarks
  
Stability
Ambient: 72 hours; Refrigerated: 1 week; Frozen: Unacceptable  
Reference Interval
By report  
Interpretive Data
Background Information for Cytochrome P450 2C19 (CYP2C19) 9 Variants:
Characteristics:
Impaired drug metabolism causing adverse drug reactions or lack of drug response. Drugs metabolized by CYP2C19 include clopidogrel, S-mephenytoin, diazepam, R-warfarin, some antidepressants (eg, citalopram, amitriptyline, clomipramine), proton pump inhibitors (eg, omeprazole, lansoprazole), and antimalarials (eg, chloroguanide).
Inheritance:
Autosomal recessive.
Cause:
CYP2C19 allelic variants.
Negative:
No variants detected is predictive of *1 functional alleles and normal enzymatic activity.
Variants Tested:
(
Variants are numbered according to NM_000769 transcript).
Decreased function: *9 (c.431G>A); *10 (c.680C>T).
Non-functional: *2 (c.681G>A), *3 (c.636G>A), *4 (c.1A>G), *6 (c.395G>A), *7 (c.819+2T>A), *8 (c.358T>C).
Increased function: *17 (c.-806C>T; increased gene transcription).
Incidence of Poor Metabolizer Phenotype:
4 percent of Caucasians, 5 percent of African Americans, and up to 25 percent of Asians.
Penetrance:
Drug dependent.
Clinical Sensitivity:
99 and 87 percent of clinically significant variants detected in Asians and Caucasians respectively; sensitivity is unknown in other ethnicities.
Methodology
: Multiplex polymerase chain reaction and detection primer extension.
Analytical Sensitivity and Specificity
: 99 percent.
Limitations
: Only the targeted CYP2C19 variants will be detected. Variants in other genes will not be detected. Diagnostic errors can occur due to rare sequence variations. Variant detection is not a substitute for therapeutic drug monitoring or other clinical monitoring.
References:
Overview of CYP's (www.anaesthestist.com); nomenclature of CYP alleles (www.cypalleles.ki.se/); drug substrates/inhibitors/inducers for CYP (http://medicine.inpui.edu/flockhart).



Counseling and informed consent are recommended for genetic testing. Consent forms are available online at www.aruplab.com.

See Compliance Statement C: www.aruplab.com/CS  
Note
 
CPT Code(s)
81225
Components
Component Test Code*Component Chart Name
0051239CYP2C19 Variant
0051240CYP2C19 Variant
0051411CYP2C19 Predicted Phenotype
2001305CYP2C19 Specimen
* Component test codes cannot be used to order tests. The information provided here is not sufficient for interface builds; for a complete test mix, please click the sidebar link to access the Interface Map.
Aliases
  • Amitriptyline
  • Clopidogrel
  • Cytochrome P450 2C19 Genotype by Sequencing Analysis, Saliva
  • Elavil
  • Escitalopram
  • Lexapro
  • Nolvadex
  • P450 2C19 Genotyping
  • Plavix
  • Tamoxifen
  • Treatment Resistant Antidepressant Panel