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- DME Genotyping
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.
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.
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.
*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.
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
Whole blood or LabCorp buccal swab kit (buccal swab collection kit contains instructions for use of a buccal swab, PeopleSoft N° 3177).
7 mL whole blood or LabCorp buccal swab kit
3 mL whole blood or two buccal swabs
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
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.