Sign in →

Test ID: 1A2V Cytochrome P450 1A2 Genotype


Specimen Required


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)/Refrigerated

 

Specimen Type: Saliva

Patient Preparation: Patient should not eat, drink smoke, or chew gum 30 minutes prior to collection.

Supplies: DNA Saliva Collection Kit (T786)

Container/Tube: Saliva Swab Collection Kit (T786: fees apply)

Specimen Volume: 1 swab

Collection Instructions: Collect and send specimen per kit instructions.

Specimen Stability Information: Ambient

 

Specimen Type: 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


Forms

1. New York Clients-Informed consent is required. Please document on the request form or electronic order that a copy is on file. An Informed Consent for Genetic Testing (T576) is available in Special Instructions.

2. If not ordering electronically, complete, print, and send a Pharmacogenomics Test Request Form (T797) with the specimen (https://www.mayomedicallaboratories.com/it-mmfiles/pharmacogenomics-test-request-form-mc0767-15.pdf)

Useful For

Identifying individuals who are poor, intermediate, normal (extensive) or rapid metabolizers of drugs metabolized by CYP1A2 to assist drug therapy decision making

Method Name

Real-Time Polymerase Chain Reaction (PCR) with Allelic Discrimination Analysis

Reporting Name

CYP1A2 Genotyping Test

Specimen Type

Varies

Specimen Minimum Volume

Blood: 0.4 mL
Saliva: 1 swab

Specimen Stability Information

Specimen Type Temperature Time
Varies Varies

Clinical Information

The cytochrome P450 (CYP) family is involved in the primary metabolism of many drugs. The CYPs are a group of oxidative/dealkylating enzymes localized in the microsomes of many tissues including the intestines and liver. One of these CYP enzymes, CYP1A2, is wholly or partially responsible for the hydroxylation or dealkylation of many commonly prescribed drugs.

 

CYP1A2-mediated drug metabolism is highly variable. A number of variants have been identified in the CYP1A2 gene that results in increased, diminished, or abolished catalytic activity and substrate metabolism. The frequency of these variants varies by ethnicity.

 

Dosing of drugs that are metabolized through CYP1A2 may require adjustment based on the CYP1A2 genotype. Individuals who are poor metabolizers may require lower than usual doses to achieve optimal response, whereas individuals who are ultrarapid metabolizers may benefit from increased doses. CYP1A2 phenotype is predicted based upon the number of functional, partially functional, nonfunctional, and inducible alleles present in a sample. In the absence of clear guidance on dosing for various metabolizer phenotypes, patients with either rapid or poor metabolism also may benefit by switching to another comparable drug that is not primarily metabolized by CYP1A2 or by therapeutic drug monitoring where applicable.

 

The following table outlines the relationship between the variations (star alleles) detected in this assay and the effect on the activity of the enzyme produced by that allele.  

CYP1A2 Allele

Nucleotide Change (Legacy nomenclature)

cDNA Nucleotide Change


Effect on Enzyme Metabolism(a)

*1

None (wild type)

None (wild type)

Normal (extensive) metabolizer

*1F

-163C->A

c.-9-154C->A

Increased inducibility

*1K

-729C->T

c.-10+113C->T

Decreased activity and decreased inducibility

*6

5090C->T

c.1291C->T

No activity

*7

3533G->A

c.1253+1G->A

No activity

 

a. Effect of a specific allele on the activity of the CYP1A2 enzyme can only be estimated since the literature does not provide precise data. 

 

A complicating factor in correlating CYP1A2 genotype to CYP1A2 phenotype is that some drugs or their metabolites are inhibitors of CYP1A2 catalytic activity. These drugs may reduce CYP1A2 catalytic activity. Consequently, an individual may require a dose decrease greater than predicted based upon genotype alone. Another complicating factor is that CYP1A2 is inducible by several drugs and environmental agents (eg, cigarette smoke) and the degree of inducibility is under genetic control. It is important to interpret the results of testing in the context of other coadministered drugs and environmental factors.

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 Human Cytochrome P450 (CYP) Allele Nomenclature Database Committee.(1)

 

CYP1A2 activity is also dependent upon hepatic function status, as well as age. Renal function may be important for drugs that are excreted in urine. Patients may develop drug toxicity if hepatic or renal function is decreased. Drug metabolism is known to decrease with age. It is important to interpret the results of testing and dose adjustments in the context of hepatic and renal function and age.

 

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

Clinical Reference

1. Human Cytochrome P450 (CYP) Allele Nomenclature Database. Accessed 5/3/2017. Available at http://www.cypalleles.ki.se/cyp1a2.htm

2. Ito M, Katono Y, Oda A, et al: Functional characterization of 20 allelic variants of CYP1A2. Drug Metab Pharmacokinet 2015 Jun;30(3):247-252

3. Zhou H, Josephy PD, Kim D, Guengerick FP: Functional characterization of four allelic variants of human cytochrome P450 1A2. Arch Biochem Biophys 2004 Feb;422(1):23-30

4. Murayama N, Soyama A, Saito Y, et al: Six novel nonsynonymous CYP1A2 gene polymorphisms: catalytic activities of the naturally occurring variant enzymes. J Pharmacol Exp Ther 2004 Jan;308(1):300-306

5. Saito Y, Hanioka N, Maekawa K, et al: Functional analysis of three CYP1A2 variants found in a Japanese population. Drug Metab Dispos 2005 Dec;33(12):1905-1910

Day(s) and Time(s) Performed

Monday through Friday, 8 a.m.

Analytic Time

3 days (Not reported Saturday or Sunday)

Test Classification

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 U.S. Food and Drug Administration.

CPT Code Information

0031U-Unlisted molecular pathology procedure

LOINC Code Information

Test ID Test Order Name Order LOINC Value
1A2V CYP1A2 Genotyping Test 80687-7

 

Result ID Test Result Name Result LOINC Value
BA0098 CYP1A2 Genotype 82939-0
BA0099 CYP1A2 Phenotype 53040-2
BA0100 Interpretation 69047-9
BA0101 Additional Information 48767-8
BA0189 Method 49549-9
BA0190 Disclaimer 62364-5
BA0102 Reviewed by 18771-6
Mayo Medical Laboratories | Genetics and Pharmacogenomics Catalog Additional Information:

mml-pgx