Cytochrome P450 2D6 Genotyping

CPT: 81226
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Test Details

Synonyms

  • DME Genotyping

Use

This testing can assist with customizing drug therapy by providing metabolic activity information that may explain patient drug responses relevant to CYP2D6 genetic variability. The cytochrome P450 (CYP450) enzymes metabolize many drugs. Individual genetic differences of cytochrome P450 activity can result in the total absence of metabolism to ultrafast metabolism of certain drugs.

Limitations

This assay does not detect other variants in the CYP2D6 gene that may affect metabolic activity. The metabolism of drugs is also influenced by race, ethnicity, diet, and medications. All factors should be considered prior to initiating new therapy. This testing does not rule out the possibility of variant alleles in other drug metabolism pathways.

Methodology

DNA analysis of the Cytochrome P450 2D6 gene (OMIM 124030) is performed using primer extension chemistry. Multiplex PCR amplifies DNA fragments containing the variants below.

Primer extension then generates a biotin-labeled product to permit flow-sorted detection of both normal and variant sequences. Molecular-based testing is highly accurate, but as in any laboratory test, rare diagnostic errors may occur.

Alleles detected:

*1, *2, *3, *4, *5, *6, *7, *8, *9, *10, *11, *15, *17, *29, *35, *41, and gene duplications.

Variant *5 is a gene deletion. Copy number of duplicated alleles is not determined. Duplications are often functional (whole gene) but may be nonfunctional (partial gene). It is not always possible to determine which allele is duplicated.

*1 represents detection of the normal sequence for the variants tested.

Additional Information

This can lead to adverse drug reactions or a lack of therapeutic effect under standard therapy conditions. CYP2D6 metabolizes 25% to 30% of all prescribed drugs.

Common drugs metabolized by 2D6 include, but are not limited to:

Opioids: Codeine, dihydrocodeine, hydrocodone, oxycodone, tramadol

Beta-blockers: Carvedilol, S-metoprolol, propafenone, propranolol, timolol

Cardioreactive drugs: Encainide, flecainide, lidocaine, mexiletine, perhexiline

Antidepressants: Amitriptyline, clomipramine, desipramine, doxepin (E-isomers), fluoxetine, fluvoxamine, imipramine, maprotiline, nortriptyline, paroxetine, sertraline, venlafaxine

Antipsychotics: Aripiprazole, haloperidol, perphenazine, risperidone, thioridazine, zuclopenthixol

Others: Tamoxifen, ondansetron, phenformin

Specimen Requirements

Specimen

Whole blood or LabCorp buccal swab kit (buccal swab collection kit contains instructions for use of a buccal swab, PeopleSoft N° 3177).

Volume

7 mL whole blood or LabCorp buccal swab kit

Minimum Volume

3 mL whole blood or two buccal swabs

Container

Lavender-top (EDTA) tube, yellow-top (ACD) tube, or LabCorp buccal swab kit

Storage Instructions

Maintain specimen at room temperature or refrigerate at 4°C.

Causes for Rejection

Frozen specimen; hemolysis; quantity not sufficient for analysis; improper container; one buccal swab; wet buccal swab

Clinical Information

Special Instructions

This test is identical in all operational aspects to test 511280. Only the report content is different, with general wording referring to the many drugs metabolized by cytochrome P450 2D6.

References

Crews KR, Gaedigk A, Dunnenberger HM, et al. Clinical Pharmacogenetics Implementation Consortium (CPIC) guidelines for cytochrome P450 2D6 genotype and codeine therapy: 2014 update. Clin Pharmacol Ther. 2014 Apr;95(4):376-382.24458010
Dutch Pharmacogenetics Working Group (DPWG) guideline information for tamoxifen and CYP2D6. 2011 www.pharmgkb.org/guideline/PA166104966.
Hicks JK, et al. Clinical pharmacogenetics implementation consortium (CPIC) guideline for CYP2D6 and CYP2C19 genotypes and dosing of tricyclic antidepressants. Clin Pharmacol Ther. 2013 May;93(5):402-408.11741249
Hicks JK, Bishop JR, Sangkuhl K, et al. Clinical pharmacogenetics implementation consortium (CPIC) guideline for CYP2D6 and CYP2C19 genotypes and dosing of selective serotonin reuptake inhibitors. Clin Pharmacol Ther. 2015 Aug;98(2):127-134.25974703
LabCorp Pharmacogenetic Testing flyer (L14582). Available upon request.
Samer CF, Lorenzini KI, Rollason V, Daali Y, Desmeules JA. Applications of CYP450 testing in the clinical setting. Mol Diagn Ther. 2013 Jun;17:165-184.23588782

LOINC® Map

Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
511230 Cytochrome P450 2D6 Genotyping 40425-1 504202 2D6 Genotype: 40425-1
511230 Cytochrome P450 2D6 Genotyping 40425-1 504203 2D6 Metabolic Activity: 79715-9
511230 Cytochrome P450 2D6 Genotyping 40425-1 504376 Interpretation: 72880-8
511230 Cytochrome P450 2D6 Genotyping 40425-1 504377 CYP2D6 Information: 49549-9
511230 Cytochrome P450 2D6 Genotyping 40425-1 504378 Cytochrome P450 2D6 Genotyping N/A

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