Test ID: HTR2O
Serotonin Receptor Genotype (HTR2A and HTR2C), Saliva
NY State Approved 
Indicates the status of NY State approval and if the test is orderable for NY State clients.
Useful For Suggests clinical disorders or settings where the test may be helpful
Guiding treatment choice of an (selective serotonin reuptake inhibitor) SSRI or non-SSRI antidepressant. Individuals homozygous for the IVS2+54538 A allele have improved probability of response to citalopram, in contrast to individuals homozygous or heterozygous for the IVS2 G allele. Individuals with major depression disorders are more likely to respond to citalopram if they are homozygous for the -1438G promoter allele.
Guiding treatment choice in individuals who have a drug-metabolizer phenotype discordant with CYP450 genotypes
Identifying patients who may benefit from treatment with the antipsychotic drug clozapine
Identifying those patients receiving atypical antipsychotic medications with excessive weight gain who may benefit by switching to different antipsychotic medications
Testing Algorithm Delineates situation(s) when tests are added to the initial order. This includes reflex and additional tests.
Special Instructions and Forms Describes specimen collection and preparation information, test algorithms, and other information pertinent to test. Also includes pertinent information and consent forms to be used when requesting a particular test
Method Name A short description of the method used to perform the test
Polymerase Chain Reaction (PCR) with Allele-Specific Primer Extension (ASPE)
(PCR is utilized pursuant to a license agreement with Roche Molecular Systems, Inc.)
Reporting Name A shorter/abbreviated version of the Published Name for a test; an abbreviated test name
Aliases Lists additional common names for a test, as an aid in searching
5HT
5HTR
HTr
HTR2A
HTR2C
Serotonin Receptor HTR
Type 2 Serotonin Receptor 5HT
Specimen Type Describes the specimen type needed for testing
Specimen Required Defines the optimal specimen. This field describes the type of specimen required to perform the test and the preferred volume to complete testing. The volume allows automated processing, fastest throughput and, when indicated, repeat or reflex testing.
Multiple saliva genotype tests can be performed on a single specimen after a single extraction. See Multiple Saliva Genotype Tests in Special Instructions for a list of tests that can be ordered together.
Container/Tube: Oragene DNA Self-Collection Kit (Supply T651)
Specimen Volume: Full tube
Collection Instructions:
1. Fill tube to line.
2. Send specimen in original container per kit instructions.
Forms: 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 (Supply T576) is available in Special Instructions.
Specimen Minimum Volume Defines the amount of specimen required to perform an assay once, including instrument and container dead space. Submitting the minimum specimen volume makes it impossible to repeat the test or perform confirmatory or perform reflex testing. In some situations, a minimum specimen volume may result in a QNS (quantity not sufficient) result, requiring a second specimen to be collected.
Reject Due To Identifies specimen types and conditions that may cause the specimen to be rejected
| Hemolysis | NA |
| Lipemia | NA |
| Icterus | NA |
| Other | NA |
Specimen Stability Information Provides a description of the temperatures required to transport a specimen to the laboratory. Alternate acceptable temperature(s) are also included.
| Specimen Type | Temperature | Time |
|---|---|---|
| Saliva | Ambient | |
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Treatment with specific antidepressant and antipsychotic medications is often guided empirically. Despite the wide array of drugs available for treatment, some patients do not initially respond to treatment, and others who respond early may eventually relapse or develop serious side effects. Antidepressant selection may be more effectively guided by genotyping polymorphic genes encoding several cytochrome P450 enzymes, the serotonin transporter, and the serotonin (5-hydroxytryptamine) receptors HTR2A and HTR2C.(1)
Drugs that bind to the serotonin receptors have a wide range of effects including altering the activation of the receptors, rendering them more or less sensitive to drug concentration, or blocking the receptor. Variations (polymorphisms) in the genes that encode for the serotonin receptor have been associated with different types of drug responses including:
-Allelic variation in the HTR2A gene has been reported to affect response to selective serotonin reuptake inhibitors (SSRI) resulting in increased drug levels and increased risk for adverse drug reactions.(2) Patients with polymorphic variants in the HTR2A/2C serotonin receptors may be considered for switching to non-SSRI antidepressants that block the type 2 receptors. Allelic variations in the HTR2A and HTR2C genes have been linked with response to the antipsychotic drug clozapine. The presence of the HTR2A receptor allele His452 has been reported to predict favorable response to clozapine therapy.(3)
-Treatment with atypical antipsychotics results in significant weight gain (2-3 kg/m[2]) in some patients. Weight gain has been positively correlated with a polymorphism in the promoter of HTR2C (-759C).(4)
-Allelic variation in the HTR2A and HTR2C genes has also been associated with increased risk of tardive dyskinesia in schizophrenic patients.(5,6)
-Allelic variation in the HTR2A gene and its promoter have been associated with improved effectiveness of citalopram in major depression disorder.
| Allele nomenclature | ||
| Gene | Nucleotide Change | Amino Acid Change |
| HTR2A | 1438G->A | Promoter polymorphism |
| HTR2A | 74C->A | Thr25Asp |
| HTR2A | IVS2+54538 A->G | Non-coding |
| HTR2A | 1354C->T | His452Tyr |
| HTR2C | -759C->T | Promoter polymorphism |
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.
Interpretation Provides information to assist in interpretation of the test results
An interpretive report will be provided.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Drug-drug interactions must be considered when dealing with heterozygous individuals.
This test does not detect polymorphisms other than those listed above.
The HTR2A gene is located on the long arm of chromosome 13 (13q). For patients with known hematologic disorders that involve deletion of 13q, call the laboratory for instructions.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Malhotra AK, Murphy GM Jr, Kennedy JL: Pharmacogenetics of psychotropic drug response. Am J Psychiatry 2004;161(5):780-796
2. Murphy GM Jr, Kremer C, Rodrigues HE, et al: Pharmacogenetics of antidepressants medication intolerance. Am J Psychiatry 2003;160(10):1830-1835
3. Arranz MJ, Murno J, Birkett J, et al: Pharmacogenetic prediction of clozapine response. Lancet 2000;355(9215):1615-1616
4. Reynolds GP, Zhang ZJ, Zhang XB: Polymorphism of the promoter region of the serotonin 5-HT2C receptor gene and clozapine-induced weight gain. Am J Psychiatry 2003;160:677-679
5. Segman RH, Heresco-Levy U, Finkel B, et al: Association between the serotonin 2A receptor gene and tardive dyskinesia in chronic schizophrenia. Mol Psychiatry 2001;6(2):225-229
6. Segman RH, Heresco-Levy U, Finkel B, et al: Association between the serotonin 2C receptor gene and tardive dyskinesia in chronic schizophrenia: additive contribution of 5-HT2Cser and DRD3gly alleles to susceptibility. Psychopharmacology 2000;152(4):408-413
7. Choi MJ, Kang RH, Ham BJ, et al: Serotonin receptor 2A gene polymorphism (-1438A->G) and short-term treatment response to citalopram. Neuropsychobiology 2005;52:155-162
8. McMahon FJ, Buervenich S, Charney D, et al: Variation in the gene encoding the serotonin 2A receptor is associated with outcome of antidepressant treatment. Am J Hum Genet 2006;78:804-814
Method Description Describes how the test is performed and provides a method-specific reference
Genomic DNA is extracted from saliva. Direct polymorphism analysis for HTR2 is performed after (multiplex) PCR and allele-specific primer extension with Luminex Molecular Diagnostics' proprietary Universal Tag sorting system on the Luminex 100 xMAP platform. A genotype is assigned based on the allele-specific fluorescent signals that are detected. (Unpublished Mayo method)
Day(s) and Time(s) Test Performed Outlines the days and times the test is performed. This field reflects the day and time the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time required before the test is performed. Some tests are listed as continuously performed, which means assays are performed several times during the day.
Wednesday; 8 a.m
Analytic Time Defines the amount of time it takes the laboratory to setup and perform the test. This is defined in number of days. The shortest interval of time expressed is "same day/1 day," which means the results may be available the same day that the sample is received in the testing laboratory. One day means results are available 1 day after the sample is received in the laboratory.
Maximum Laboratory Time Defines the maximum time from specimen receipt at Mayo Medical Laboratories until the release of the test result
Specimen Retention Time Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
Performing Laboratory Location The location of the laboratory that performs the test
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's instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR), Investigation Use Only (IUO) product, or a Research Use Only (RUO) product.
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 Medical Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
81479 -Unlisted molecular pathology procedure
LOINC® Code Information Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the result codes returned for this test or profile.
| Result ID | Reporting Name | LOINC Code |
|---|---|---|
| 32936 | HTR2A -1438G>A | In Process |
| 32937 | HTR2A 74C>A | In Process |
| 32938 | HTR2A 102 T>C | In Process |
| 32939 | HTR2A IVS2 A>G | In Process |
| 32940 | HTR2A 1354 C>T | In Process |
| 32941 | HTR2C -759 C>T | In Process |
| 32942 | HTR2C 796 G>C | In Process |
| 32943 | Reviewed By | In Process |
| 32944 | HTR2 Genotype | In Process |
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