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HelpTest ID: 2B6Q Cytochrome P450 2B6 Genotype, Varies
Ordering Guidance
Testing is available as the single gene assay (this test) and as a part of a psychotropic pharmacogenomics panel.
If genotype testing for psychotropic medications is requested, order PSYQP / Psychotropic Pharmacogenomics Gene Panel, Varies.
Specimen Required
Patient Preparation: A previous hematopoietic stem cell transplant from an allogenic donor or a liver transplant will interfere with testing. For information about testing patients who have received a hematopoietic stem cell or liver transplant call 800-533-1710.
Submit only 1 of the following specimens:
Specimen Type: Whole blood
Container/Tube: Lavender top (EDTA)
Specimen Volume: 3 mL
Collection Instructions:
1. Invert several times to mix blood.
2. Send whole blood specimen in original tube. Do not aliquot.
Specimen Stability Information: Ambient (preferred) 4 days/Refrigerated 4 days/Frozen 4 days
Additional Information:
1. Specimens are preferred to be received within 4 days of collection. Extraction will be attempted for specimens received after 4 days, and DNA yield will be evaluated to determine if testing may proceed.
2. To ensure minimum volume and concentration of DNA are met, the requested volume must be submitted. Testing may be canceled if DNA requirements are inadequate.
Specimen Type: Cord blood
Container/Tube: Lavender top (EDTA)
Specimen Volume: 3 mL
Collection Instructions:
1. Invert several times to mix blood.
2. Send cord blood specimen in original tube. Do not aliquot.
Specimen Stability Information: Ambient (preferred) 4 days/Refrigerated 4 days/Frozen 4 days
Additional Information:
1. Specimens are preferred to be received within 4 days of collection. Extraction will be attempted for specimens received after 4 days, and DNA yield will be evaluated to determine if testing may proceed.
2. To ensure minimum volume and concentration of DNA are met, the requested volume must be submitted. Testing may be canceled if DNA requirements are inadequate.
3. While a properly collected cord blood sample may not be at risk for maternal cell contamination, unanticipated complications may occur during collection. Therefore, maternal cell contamination studies are recommended to ensure the test results reflect that of the patient tested and are available at an additional charge. Order MATCC / Maternal Cell Contamination, Molecular Analysis, Varies on the maternal specimen.
Specimen Type: Saliva
Patient Preparation: Patient should not eat, drink, smoke, or chew gum 30 minutes prior to collection.
Supplies: Saliva Swab Collection Kit (T786)
Specimen Volume: 2 Swabs
Collection Instructions: Collect and send specimen per kit instructions.
Specimen Stability Information: Ambient (preferred) 30 days/Refrigerated 30 days
Additional Information: Saliva specimens are acceptable but not recommended. Due to lower quantity/quality of DNA yielded from saliva, some aspects of the test may not perform as well as DNA extracted from a whole blood sample. When applicable, specific gene regions that were unable to be interrogated will be noted in the report. Alternatively, additional specimen may be required to complete testing.
Specimen Type: Extracted DNA
Container/Tube:
Preferred: Screw Cap Micro Tube, 2 mL with skirted conical base
Acceptable: Matrix tube, 1 mL
Collection Instructions:
1. The preferred volume is at least 100 mcL at a concentration of 75 ng/mcL.
2. Include concentration and volume on tube.
Specimen Stability Information: Frozen (preferred) 1 year/Ambient/Refrigerated
Additional Information: DNA must be extracted in a CLIA-certified laboratory or equivalent and must be extracted from a specimen type listed as acceptable for this test (including applicable anticoagulants). Our laboratory has experience with Chemagic, Puregene, Autopure, MagnaPure, and EZ1 extraction platforms and cannot guarantee that all extraction methods are compatible with this test. If testing fails, one repeat will be attempted, and if unsuccessful, the test will be reported as failed and a charge will be applied. If applicable, specific gene regions that were unable to be interrogated due to DNA quality will be noted in the report.
Forms
1. New York Clients-Informed consent is required. Document on the request form or electronic order that a copy is on file. The following documents are available:
-Informed Consent for Genetic Testing (T576)
-Informed Consent for Genetic Testing-Spanish (T826)
2. If not ordering electronically, complete, print, and send a Therapeutics Test Request (T831) with the specimen.
Useful For
Aiding in determining therapeutic strategies for drugs that are metabolized by cytochrome P450 (CYP) 2B6
Providing information relevant to efavirenz and sertraline, as well as other medications metabolized by CYP2B6
Determining the genotype if genotype-phenotype discord is encountered clinically after testing with a less comprehensive genotyping method has occurred
Identifying a genotype when required for drug trials and research protocols
Special Instructions
Method Name
Real Time-Polymerase Chain Reaction (RT-PCR) with Allelic Discrimination Analysis
Reporting Name
CYP2B6 Genotype, VSpecimen Type
VariesSpecimen Minimum Volume
See Specimen Required
Specimen Stability Information
| Specimen Type | Temperature | Time |
|---|---|---|
| Varies | Varies | |
Clinical Information
The cytochrome P450 (CYP) family of enzymes is a group of oxidative/dealkylating enzymes localized in the microsomes of many tissues including the intestines and liver. CYP2B6 is wholly or partially responsible for the metabolism of several commonly prescribed drugs.
The CYP2B6 gene is highly variable with over 38 named alleles. This gene can have multiple sequence variations. Alleles thought to have an impact upon CYP2B6 enzyme function at the time that this test was developed are included in this test (see Table). Individuals without a detectable gene alteration will be reported as CYP2B6*1/*1, but it is possible that these individuals harbor unknown variants that may impact metabolism. In addition, some individuals have genes that are hybrids of CYP2B6 and the CYP2B7 pseudogene. The frequency of these hybrids is unknown, and this assay does not test for these hybrids.
Star allele genotypes are called based on the Pharmacogene Variation Consortium definitions (1) CYP2B6 genotype results are used to predict metabolizer phenotypes based on the Clinical Pharmacogenetics Implementation Consortium published guidelines.(2,3) A CYP2B6 phenotype is predicted based upon the number of functional, partially functional, and nonfunctional alleles present in a sample. In rare instances where alleles with unknown function are present in a homozygous or compound heterozygous state, an unknown phenotype occurs and a range is provided.
Several medications act as substrates of CYP2B6. CYP2B6-metabolized medications with published guidelines for the use of CYP2B6 genotype to guide medication use include efavirenz and sertraline.(2-4) While methadone is known to be metabolized by CYP2B6, the data do not consistently demonstrate that variation in CYP2B6 clinically impacts methadone efficacy or toxicity and a guideline suggests that no change in dosing based on CYP2B6 genotype is required.(5) Bupropion, ketamine, and nevirapine are also known to be metabolized by CYP2B6, but no dosing guidelines are available. Other enzymes may be involved in the metabolism of these drugs.
There is a variable degree of substrate specificity exhibited by CYP2B6 alleles on these medications. This means that the same allele (ie, *6) may not metabolize all substrates at exactly the same rate.
Drugs that are metabolized by CYP2B6 may require dosage adjustment based on the individual patient's genotype. For example, patients who are poor metabolizers may require much lower than usual doses to achieve optimal response in the case of drugs that are inactivated by the CYP2B6 enzyme. Alternatively, patients who are ultrarapid metabolizers may benefit from increased doses in the case of drugs that are inactivated by CYP2B6 enzyme. In the absence of clear guidance from the US Food and Drug Administration on dosing for various metabolizer phenotypes, patients with either ultrarapid or poor metabolism may benefit by switching to comparable alternate medications that are not primarily metabolized by CYP2B6 or by therapeutic drug monitoring where applicable.
Table. Function of Individual Star Alleles
|
Enzyme function |
Examples of CYP2B6 star alleles |
|
Normal function |
*1, *5 |
|
Increased function |
*4 |
|
Decreased function |
*6, *7, *9, *19, *20, *26, *36 |
|
No or null function |
*8, *12, *13, *16 (also known as *18.002), *18, *38 |
|
Uncertain function |
*11, *14, *15, *22, *27, *35 |
Reference Values
An interpretive report will be provided.
Interpretation
An interpretive report will be provided.
The genotype, with associated star alleles, is assigned using standard allelic nomenclature as published by the Pharmacogene Variation (PharmVar) Consortium.(1)
For additional information regarding pharmacogenomic genes and their associated drugs, see Pharmacogenomic Associations Tables. This resource also includes information regarding enzyme inhibitors and inducers, as well as potential alternate drug choices.
Clinical Reference
1. PharmVar. Pharmacogene Variation Consortium. Updated March 3, 2021. Accessed May 12, 2025. Available at www.pharmvar.org/
2. Clinical Pharmacogenetics Implementation Consortium (CPIC). Accessed May 12, 2025. Available at https://cpicpgx.org/
3. Desta Z, Gammal RS, Gong L, et al. Clinical Pharmacogenetics Implementation Consortium (CPIC) Guideline for CYP2B6 and Efavirenz-Containing Antiretroviral Therapy. Clin Pharmacol Ther. 2019;106(4):726-733. doi:10.1002/cpt.1477
4. Bousman CA, Stevenson JM, Ramsey LB, et al. Clinical Pharmacogenetics Implementation Consortium (CPIC) Guideline for CYP2D6, CYP2C19, CYP2B6, SLC6A4, and HTR2A Genotypes and Serotonin Reuptake Inhibitor Antidepressants. Clin Pharmacol Ther. 2023;114(1):51-68
5. Robinson KM, Eum S, Desta Z, et al. Clinical Pharmacogenetics Implementation Consortium Guideline for CYP2B6 Genotype and Methadone Therapy. Clin Pharmacol Ther. 2024;116(4):932-938
Day(s) Performed
Varies
Report Available
3 to 8 daysTest Classification
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.CPT Code Information
81479
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| 2B6Q | CYP2B6 Genotype, V | 72511-9 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| 610082 | CYP2B6 Genotype | 72882-4 |
| 610083 | CYP2B6 Phenotype | 79720-9 |
| 610566 | CYP2B6 Activity Score | 104666-3 |
| 610084 | Interpretation | 69047-9 |
| 610085 | Additional Information | 48767-8 |
| 610086 | Method | 85069-3 |
| 610087 | Disclaimer | 62364-5 |
| 610088 | Reviewed by | 18771-6 |
Reflex Tests
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| MATCC | Maternal Cell Contamination, B | Yes | No |
Testing Algorithm
For cord blood specimens that have an accompanying maternal blood specimen, maternal cell contamination studies will be performed at an additional charge.
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