Cytochrome P450 1A2 (CYP1A2) Genotyping
Test Code
Cytochrome P450 1A2 (CYP1A2)
CPT Codes
83891 x1; 83898 x2; 83892 x2; 83894 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
CYP1A2 metabolizes many medications, including theophylline, diazepam, caffeine, and amitriptyline. CYP1A2 can be induced by several medications, substrates, and constituents of tobacco smoke. CYP1A2 can also be inhibited by several medications. Basal metabolic capacity remains relatively consistent among the different genotypes in the absence of an inducer. Detecting variants of the CYP1A2 gene that cause altered enzymatic induction in the presence of an inducer can identify patients who may be at increased risk of having adverse drug reactions or therapeutic failure to standard dosages of CYP1A2 substrates.
Limitations
Other variants of the CYP1A2 gene that are not detected in this assay may influence drug metabolism. CYP1A2 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
Polymerase chain reaction and restriction fragment polymorphism analysis (PCR-RFLP).
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.
Chida M et al. Detection of three genetic polymorphisms in the 5’ flanking region and intron 1 of human CYP1A2 in the Japanese population. Jpn J Cancer Res 1999; 90:899-902.
Hamdy SI et al. Genotyping of four genetic polymorphisms in the CYP1A2 gene in the Egyptian population. Br J Clin Pharmacol 2003; 55:321-324.
Sachse C et al. Functional significance of a C>A polymorphism in intron 1 of the cytochrome P450 CYP1A2 gene tests with caffeine. Br J Clin Pharmacol 1999;47:445-449.
Eap CB et al. Nonresponse to clozapine and ultrarapid CYP1A2 activity: clinical data and analysis of CYP1A2 gene. J Clin Psychopharmacol 2004;24(2):214-219.
Soyama A et al. Single nucleotide polymorphisms and haplotypes of CYP1A2 in a Japanese population. Drug Metab Pharmacokinet 2005;20(1):24-33.