Test Catalog

Test Id : 3A4Q

Cytochrome P450 3A4 Genotype, Varies

Useful For
Suggests clinical disorders or settings where the test may be helpful

Aids in determining therapeutic strategies for drugs that are metabolized by cytochrome P450 3A4, including atorvastatin, simvastatin, and lovastatin


This test is not useful for managing patients receiving fluvastatin, rosuvastatin, or pravastatin since these drugs are not metabolized appreciably by CYP3A4.

Special Instructions
Library of PDFs including pertinent information and forms related to the test

Method Name
A short description of the method used to perform the test

Polymerase Chain Reaction (PCR) With Allelic Discrimination Analysis

NY State Available
Indicates the status of NY State approval and if the test is orderable for NY State clients.


Reporting Name
Lists a shorter or abbreviated version of the Published Name for a test

CYP3A4 Genotype, V

Lists additional common names for a test, as an aid in searching



Cytochrome P450 3A4 (CYP3A4) Genotyping

Specimen Type
Describes the specimen type validated for testing


Ordering Guidance

Testing is available as the single gene assay (this test) and as a part of a psychotropic or focused pharmacogenomics panel.


If multiple pharmacogenomic genotype testing is desired, order PGXQP / Focused Pharmacogenomics Panel, Varies.


If genotype testing for psychotropic medications is desired, order PSYQP / Psychotropic Pharmacogenomics Gene Panel, Varies.

Additional Testing Requirements

Most drugs metabolized by CYP3A4 are also metabolized by CYP3A5, but usually to a lesser extent, so testing of CYP3A5 may also be relevant and should be determined on a case by case basis. If CYP3A5 genotyping is needed, order 3A5Q / Cytochrome P450 3A5 Genotype, Varies.

Specimen Required
Defines the optimal specimen required to perform the test and the preferred volume to complete testing

Multiple genotype tests can be performed on a single specimen after a single extraction. See Multiple Genotype Test List in Special Instructions for a list of tests that can be ordered together.


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 specimen in original tube.

Specimen Stability Information: Ambient (preferred) 9 days/Refrigerated 30 days


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: One swab

Collection Instructions: Collect and send specimen per kit instructions.

Specimen Stability Information: Ambient 30 days


Specimen Type: Extracted DNA

Container/Tube: 2 mL screw top tube

Specimen Volume: 100 mcL (microliters)

Collection Instructions:

1. The preferred volume is 100 mcL at a concentration of 50 ng/mcL.

2. Include concentration and volume on tube.

Specimen Stability Information: Frozen (preferred)/Ambient/Refrigerated

Special Instructions
Library of PDFs including pertinent information and forms related to the test


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 in Special Instructions:

-Informed Consent for Genetic Testing (T576)

-Informed Consent for Genetic Testing-Spanish (T826)

2. If not ordering electronically, complete, print, and send 1 of the following forms with the specimen:

-Pharmacogenomics Test Request (T797)

-Cardiovascular Test Request (T724)

-Neurology Specialty Testing Client Test Request (T732)

-Therapeutics Test Request (T831)

Specimen Minimum Volume
Defines the amount of sample necessary to provide a clinically relevant result as determined by the testing laboratory. The minimum volume is sufficient for one attempt at testing.

Blood: 0.4 mL

Saliva: 1 swab

Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected

All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.

Specimen Stability Information
Provides a description of the temperatures required to transport a specimen to the performing laboratory, alternate acceptable temperatures are also included

Specimen Type Temperature Time Special Container
Varies Varies

Useful For
Suggests clinical disorders or settings where the test may be helpful

Aids in determining therapeutic strategies for drugs that are metabolized by cytochrome P450 3A4, including atorvastatin, simvastatin, and lovastatin


This test is not useful for managing patients receiving fluvastatin, rosuvastatin, or pravastatin since these drugs are not metabolized appreciably by CYP3A4.

Clinical Information
Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

CYP3A4 is a member of the CYP3A family of genes located on chromosome 7. The cytochrome P450 (CYP) 3A subfamily of enzymes is responsible for the metabolism of more than 50% of medications that undergo hepatic metabolism and first-pass metabolism in intestinal epithelial cells, including some lipid-lowering drugs. The CYP3A4 enzyme activity is highly variable. Interindividual differences in enzyme expression may be due to several factors including: variable homeostatic control mechanisms, disease states that alter homeostasis, up- or down-regulation by environmental stimuli, and genetic variation.(1)


One variant, CYP3A4*22 (c.522-191C>T), has been studied extensively. This variant affects hepatic expression of CYP3A4 and response to statin drugs. The CYP3A4*22 allele is associated with reduced CYP3A4 activity, which may result in a better response to lipid-lowering drugs, such as simvastatin, atorvastatin, or lovastatin. However, reduced CYP3A4 activity may also be associated with statin-induced myopathy, especially for simvastatin. Studies show that in livers with the reference (wild-type) genotype (homozygous C or CC) the CYP3A4 mRNA level and enzyme activity were 1.7- and 2.5-fold greater than in CYP3A4*22 heterozygotes (CT) and homozygotes (TT), respectively. In 235 patients taking stable doses of drugs for lipid control, carriers of the T allele required significantly lower statin doses for optimal lipid control than did non-T carriers.(2) These results indicate that CYP3A4*22 markedly affects expression of CYP3A4 and could serve as a biomarker for CYP3A4 metabolizer phenotype. The reported allele frequency of CYP3A4*22 is 5% to 8% in the white population and 4.3% in African American and Chinese populations.


Other alleles have not been as extensively studied in clinical trials but are expected to have similar impacts on statin metabolism and the metabolism of other drugs primarily metabolized by CYP3A4.


The following table displays the CYP3A4 variants detected by this assay, the corresponding star allele, and the effect on CYP3A4 enzyme activity. Individuals without a detectable CYP3A4 variant are designated as CYP3A4*1/*1.

CYP3A4 allele

cDNA nucleotide change


Effect on enzyme activity


None (wild type)

Normal activity



No activity



Reduced activity



Reduced activity



No activity



Minimal activity



No activity



Reduced activity



Reduced activity



No activity


Genotype to phenotype predictions are based on the Pharmacogene Variation Consortium website (3) and review of the CYP3A4 literature.

Reference Values
Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

An interpretive report will be provided.

Provides information to assist in interpretation of the test results

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.(3)


For additional information regarding pharmacogenomic genes and their associated drugs, see the Pharmacogenomics Associations Tables in Special Instructions. This resource also includes information regarding enzyme inhibitors and inducers, as well as potential alternate drug choices.

Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Rare variants may be present that could lead to false-negative or false-positive results. If results obtained do not match the clinical findings, additional testing could be considered.


Samples may contain donor DNA if obtained from patients who received non-leukoreduced blood transfusions or allogeneic hematopoietic stem cell transplantation. Results from samples obtained under these circumstances may not accurately reflect the recipient's genotype. For individuals who have received blood transfusions, the genotype usually reverts to that of the recipient within 6 weeks. For individuals who have received allogeneic hematopoietic stem cell transplantation, a pretransplant DNA specimen is recommended for testing.


CYP3A4 genetic test results in patients who have undergone liver transplantation may not accurately reflect the patient's CYP3A4 status.


This test does not detect all variants that result in altered CYP3A4 activity. Therefore, absence of a detectable variant does not rule out the possibility that a patient has altered CYP3A4 metabolism due to other CYP3A4 variants that cannot be detected with this method. Furthermore, when 2 or more variants are identified, the cis-/trans- status (whether the variants are on the same or opposite chromosomes) is not always known.


Drug-drug interactions and drug-metabolite inhibition must be considered.


Drug-metabolite inhibition can occur, resulting in inhibition of CYP3A4 catalytic activity.


Patients may also develop toxicity problems if liver and kidney function are impaired.

Clinical Reference
Recommendations for in-depth reading of a clinical nature

1. Evans WE, Relling MV. Pharmacogenomics: translating functional genomics into rational therapeutics. Science. 1999;286(5439):487-491. doi: 10.1126/science.286.5439.487

2. Wang D, Guo Y, Wrighton SA, Cooke GE, Sadee W. Intronic polymorphism in CYP3A4 affects hepatic expression and response to statin drugs. Pharmacogenomics J. 2011;11(4):274-286. doi:10.1038/tpj.2010.28

3. PharmVar: Pharmacogene Variation Consortium. Updated March 3, 2021. Accessed March 22, 2021. Available at www.pharmvar.org/

4. Lamba JK, Lin YS, Schuetz EG, Thummel KE. Genetic contribution to variable human CYP3A-mediated metabolism. Adv Drug Deliv Rev. 2002;54(10):1271-1294. doi: 10.1016/s0169-409x(02)00066-2

5. Elens L, Becker ML, Haufroid V, et al. Novel CYP3A4 intron 6 single nucleotide polymorphism is associated with simvastatin-mediated cholesterol reduction in the Rotterdam Study. Pharmacogenet Genomics. 2011;21(12):861-866. doi: 10.1097/FPC.0b013e32834c6edb

6. Elens L, van Schaik RH, Panin N, et al. Effect of a new functional CYP3A4 polymorphism on calcineurin inhibitors' dose requirements and trough blood levels in stable renal transplant patients. Pharmacogenomics. 2011;12(10):1383-1396. doi: 10.2217/pgs.11.90

7. Clinical Pharmacogenetics Implementation Consortium (CPIC). Accessed October 14, 2020. https://cpicpgx.org/

Special Instructions
Library of PDFs including pertinent information and forms related to the test

Method Description
Describes how the test is performed and provides a method-specific reference

Genomic DNA is extracted from whole blood or saliva. Genotyping for the CYP3A4 alleles is performed using a polymerase chain reaction (PCR)-based 5'-nuclease assay. Fluorescently labeled detection probes anneal to the target DNA. PCR is used to amplify the section of DNA that contains the variant. If the detection probe is an exact match to the target DNA, the 5'-nuclease polymerase degrades the probe, the reporter dye is released from the effects of the quencher dye, and a fluorescent signal is detected. Genotypes are assigned based on the allele-specific fluorescent signals that are detected.(Unpublished Mayo method)

PDF Report
Indicates whether the report includes an additional document with charts, images or other enriched information


Day(s) Performed
Outlines the days the test is performed. This field reflects the day that the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time before the test is performed. Some tests are listed as continuously performed, which means that assays are performed multiple times during the day.

Monday through Friday

Report Available
The interval of time (receipt of sample at Mayo Clinic Laboratories to results available) taking into account standard setup days and weekends. The first day is the time that it typically takes for a result to be available. The last day is the time it might take, accounting for any necessary repeated testing.

3 to 8 days

Specimen Retention Time
Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded

Whole Blood/Saliva Swab: 2 weeks; Extracted DNA: 2 months

Performing Laboratory Location
Indicates the location of the laboratory that performs the test


Several factors determine the fee charged to perform a test. Contact your U.S. or International Regional Manager for information about establishing a fee schedule or to learn more about resources to optimize test selection.

  • Authorized users can sign in to Test Prices for detailed fee information.
  • Clients without access to Test Prices can contact Customer Service 24 hours a day, seven days a week.
  • Prospective clients should contact their account representative. For assistance, contact Customer Service.

Test Classification
Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR) product.

This test was developed, and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information
Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Clinic Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.

CPT codes are provided by the performing laboratory.


LOINC® Information
Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the order and results codes of this test. LOINC values are provided by the performing laboratory.

Test Id Test Order Name Order LOINC Value
3A4Q CYP3A4 Genotype, V 74007-6
Result Id Test Result Name Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
610110 CYP3A4 Genotype 81139-8
610111 CYP3A4 Phenotype 81145-5
610112 Interpretation 69047-9
610113 Additional Information 48767-8
610114 Method 85069-3
610115 Disclaimer 62364-5
610116 Reviewed by 18771-6

Test Setup Resources

Setup Files
Test setup information contains test file definition details to support order and result interfacing between Mayo Clinic Laboratories and your Laboratory Information System.

Excel | Pdf

Sample Reports
Normal and Abnormal sample reports are provided as references for report appearance.

Normal Reports | Abnormal Reports

SI Sample Reports
International System (SI) of Unit reports are provided for a limited number of tests. These reports are intended for international account use and are only available through MayoLINK accounts that have been defined to receive them.

SI Normal Reports | SI Abnormal Reports