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Cytochrome P450 2C19 (CYP2C19) Genotyping

Test Code

Cytochrome P450 2C19 (CYP2C19)

CPT Codes

83891 x1; 83892 x2; 83900 x1; 83901 x3; 83914 x7; 83909 x1; 83912 x1; 83912-25 x1

Specimen

Whole blood or buccal swabs

Volume

5 mL of whole blood or four buccal swabs

Minimum Volume

3 mL of whole blood or four buccal swabs

Container

Lavender-stopper (EDTA) tube or paper envelope for dried buccal swabs

Storage Instructions

Maintain at room temperature or refrigerate

Cause for Rejection

Hemolyzed specimen; quantity not sufficient

Use

CYP2C19 metabolizes approximately 10% of all drugs, including citalopram, diazepam, and many of the proton pump inhibitors. Detecting variants of the CYP2C19 gene that cause altered enzymatic activity can identify patients who may be at increased risk of having adverse drug reactions or therapeutic failure to standard dosages of CYP2C19 substrates.

Limitations

Other variants of the CYP2C19 gene that are not detected in this assay may influence drug metabolism. CYP2C19 metabolic capacity is also influenced by concomitant medications, inhibitors, inducers, diet and various disease states. All factors should be considered as part of the overall patient management strategy.

Methodology

Multiplex polymerase chain reaction and allele-specific primer extension (Tag-It (TM)).

Turnaround Time

Five business days after receipt of specimen. STAT turnaround time of 3 business days is available for an additional charge.

References

Phillips KA et al. Potential role of pharmacogenetics in reducing adverse drug reactions: a systemic review. JAMA 2001;286(18):2270-2279.