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Houston, Texas

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Medical Genetics Test Details

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Cytochrome P450 2D6 (CYP2D6) Genotyping
Test Information: This analysis tests 16 different variants associated with altered CYP2D6 activity.

Reasons for testing:
Evaluating genetic factors affecting drug metabolism for patients taking antidepressant drugs and other drugs metabolized by CYP2D6.

Evaluating genetic factors affecting drug metabolism for patients considering or taking Tamoxifen chemotherapy.
Test Details
Test Code: 6875
Test Includes: Variant alleles tested:

2 (2850C>T): normal activity
2A (-1584C>G): normal activity
3 (2549delA): no activity
4 (1846G>A): no activity
5 (deletion): no activity
6 (1707delT): no activity
7 (2935A>C): no activity
8 (1758G>T): no activity
9 (2613_2615delAGA): decreased activity
10 (100C>T): decreased activity
12 (124G>A): no activity
14 (1758G>A): no activity
17 (1023C>T): decreased activity
29 (1659G>A): decreased activity
41 (2988G>A): decreased activity
XN (Gene Duplication): increased activity


Special Notes: The following are examples of pharmaceutical agents that may be affected by CYP2D6 genotype:

1. Agents to treat depression: These include the class of drugs known as selective serotonin reuptake inhibitors (SSRI) and tricyclic anitdepressants. Individuals who have two copies of inactivating 2D6 variations are referred to as poor metabolizers. These individuals may require lower than usual doses to achieve safety and efficacy. Individuals who have two copies of variations resulting in increased activity are referred to as ultra-rapid metabolizers who may need increased drug dosages.

2. Tamoxifen: Tamoxifen is a selective estrogen receptor modulator that binds to the estrogen receptor and is used in the treatment of estrogen-receptor positive breast cancer. Tamoxifen is metabolized by CYP2D6 to an active form that has much higher affinity for the estrogen receptor than does Tamoxifen. Individuals who are CYP2D6 poor metabolizers and are taking Tamoxifen may have decreased levels of the active metabolite and thus may have decreased efficacy of the drug and a higher frequency of breast cancer relapse. Increasing the dose of Tamoxifen in poor metabolizer patients does not appear to improve outcomes for this group of patients.

Limitations:
1. Not all variants with known impact on enzyme expression and activity are tested in this assay.
2. Non-genetic factors, variations in the other genes involving the drug metabolism are not measured by this assay.
3. Rare genetic alterations at primer binding sites may result diagnostic errors.

Technical Information
Methodology: This analysis incorporates DNA amplification by multiplex PCR, allele specific primer extension, microarray hybridization and Fluorescence signal detection.
Gene Name: CYP2D6
References Values or Ranges: Analytical Sensitivity and Specificity: Greater than 99%
Sample & Shipping Information
Test Requisition: Molecular Diagnostics
Specimen Type: Blood
Requirements: Draw blood in an EDTA (purple-top) tube(s) and send 3 cc (Adults)
Shipping Conditions: Ship at room temperature in an insulated container by overnight courier. Do not heat or freeze.

Turn Around Time: 14 days
Billing Information
List Price: *For Insurance or Institutional Prices, please call.
CPT Codes: 81226x1


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