Test ID: HTR2
Serotonin Receptor Genotype (HTR2A and HTR2C)
Secondary ID 
A test code used for billing and in test definitions created prior to November 2011
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 antidepressant and antipsychotic drug selection
Identifying patients who may benefit from treatment with the antipsychotic drug clozapine
Identifying those patients receiving antipsychotic medications at risk for excessive weight gain
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 whole blood EDTA genotype tests can be performed on a single specimen after a single extraction. See Multiple Whole Blood EDTA Genotype Tests in Special Instructions for a list of tests that can be ordered together.
Container/Tube: Lavender top (EDTA)
Specimen Volume: 3 mL
Additional Information:
1. Bone marrow transplants will interfere with testing. Call Mayo Medical Laboratories at 800-533-1710 or 507-266-5700 for instructions.
2. Transfusions will interfere with testing for up to 4 to 6 weeks. DNA obtained from white cells may not provide useful information for patients who received a recent transfusion of blood that was not leukocyte-reduced. Wait 4 to 6 weeks until transfused cells have left the patient's circulation before drawing the patient's blood specimen for genotype testing.
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 |
|---|---|---|
| Whole Blood EDTA | Ambient (preferred) | |
| Refrigerated | ||
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:
-HTR2A receptor
- The -1439A->G polymorphism is associated with SSRI response and side effects and antipsychotic response. The GG genotype responds better and has higher adverse drug reactions to SSRI than the AG or AA genotypes.(1) The GG genotype is also associated with poorer response to clozapine and typical antipsychotics.(2)
- The 74C->A polymorphism has not been studied in vivo but in vitro studies show that the A allele causes a 30 fold decrease in aripiprazole agonist potency so individuals with the A allele are expected to respond poorly to the drug.(3)
- The IVS2+5453A->G polymorphism is associated with citalopram response. The GG genotype responds to citalopram poorer than the AA genotype.(4)
- For the 1354C->T polymorphism, the TT and CT genotypes are associated with poorer response to clozapine.(5)
-HTR2C receptor
- For the -759C->T polymorphism, the CT or TT genotypes are associated with less weight gain caused by antipsychotic administration.(6-7)
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). Patients identified with hematologic disorders that involve deletion of 13q should call the laboratory for instructions.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Kato M, Serretti A: Review and meta-analysis of antidepressant pharmacogenetic findings in major depressive disorder. Molecular Psychiatry 2010;15:473-500
2. Arranz MJ, Murno J, Birkett J, et al: Pharmacogenetic prediction of clozapine response. Lancet 2000;355(9215):1615-1616
3. Davies MA, Setola V, Strachan RT, et al: Pharmacologic analysis of non-synonymous coding h5-HT(2A) SNPs reveals alterations in atypical antipsychotic and agonist efficacies. Pharmacogenomics Journal, 2006;6:42-51
4. 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
5. Masellis M, Basile V, Meltzer HY, et al: Serotonin subtype 2 receptor genes and clinical response to clozapine in schizophrenia patients. Neuropsychopharmacology, 1998;19:123-132
6. 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
7. Templeman LA, Reynolds GP, Arranz B, San L: Polymorphisms of the 5-HT2C receptor and leptin genes are associated with antipsychotic drug-induced weight gain in Caucasian subjects with a first-episode psychosis. Pharmacogenetics and Genomics, 2005;15(4):195-200
Method Description Describes how the test is performed and provides a method-specific reference
Genomic DNA is extracted from whole blood. Direct polymorphism analysis for HTR2 is performed after (multiplex) PCR and allele-specific primer extension (ASPE) 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 |
|---|---|---|
| 83303 | HTR2 Genotype | In Process |
| 28352 | HTR2A -1438G>A | In Process |
| 26323 | HTR2A 74C>A | In Process |
| 28054 | HTR2A 102 T>C | In Process |
| 28353 | HTR2A IVS2 A>G | In Process |
| 26324 | HTR2A 1354 C>T | In Process |
| 19497 | HTR2C -759 C>T | In Process |
| 26325 | HTR2C 796 G>C | In Process |
| 26326 | Reviewed By | In Process |
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