Test ID: HTT
Serotonin Transporter Genotype, Blood
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
Evaluating patients who have failed therapy with selective serotonin reuptake inhibitors (SSRIs)
Evaluating patients with treatment-resistant depression
Predicting response time to improvement with SSRIs
Identifying patients who might respond favorably to a class of antidepressants other than SSRI.
Identifying patients who have diminished amounts of the serotonin transporter and, hence, an altered response to SSRI therapeutics
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) Followed by Sizing Analysis
(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
5-HT transporter, LPR
5-HTT
5HT transporter
5HT transporter, LPR
5HTT
hSERT
OCD1
Serotonin dependent transporter
Serotonin transporter (SERT)
Serotonin transporter promoter
SERT (Serotonin transporter)
SLC6A4 (solute carrier family 6 [neurotransmitter, serotonin])
Sodium-dependent serotonin receptor
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
Serotonin (5-hydroxytryptamine; 5-HT) is a neurotransmitter. The serotonin transporter (5-HTT) modulates neurotransmission by facilitating removal of serotonin from the synapse of serotonergic neurons, resulting in serotonin reuptake into the presynaptic terminus. Other designations for 5-HTT are SLC6A4 (solute carrier family 6 [neurotransmitter transporter, serotonin], member 4), hSERT, OCD1, SERT, sodium-dependent serotonin transporter, and 5-HT transporter.
Selective serotonin reuptake inhibitors (SSRIs) block the action of the serotonin transporter and are used to treat depression and other neuropsychiatric disorders. Examples of SSRIs are fluoxetine (Prozac), fluvoxamine (Luvox), escitalopram oxalate (Lexapro), sertraline (Zoloft), citalopram (Celexa), and paroxetine (Paxil, Paxil CR).
The 5-HTT gene is located at 17q11.1-q12 and is composed of 14 exons spanning 31 kb. A 44-base pair promoter insertion/deletion polymorphism called LPR, or linked polymorphic region, produces alleles described as long or short. The short allele is dominant and results in decreased concentration of the transporter protein and a poorer response to stressful events. While individuals homozygous for the long allele (l/l) may demonstrate response to SSRI therapy in 3 to 4 weeks, individuals with the short allele (l/s or s/s) may respond to SSRI therapy more slowly, taking up to 12 weeks.
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
The normal (wildtype) allele yields a long product (l/l). The variant is short/short (s/s). Heterozygotes have a l/s genotype.
Individuals homozygous for the long allele (l/l) may respond more rapidly to selective serotonin reuptake inhibitors (SSRI) therapy.
Individuals homozygous for the short allele (s/s) may respond more slowly to SSRI therapy and may benefit from a longer trial before considering switching to another antidepressant. Even 1 copy of the short allele (heterozygous) decreases the amount of the transporter protein present, increasing the time to response.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
The test measures only the 5-HTT (LPR) polymorphism and will not indicate the presence of any other polymorphism. A mutation occurring at the site of PCR primer annealing could lead to a heterozygote being incorrectly labeled as a homozygote.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Lesch KP, Gutnecht L: Pharmacogenetics of the serotonin transporter. Prog Neuropsychopharmacol Biol Psychiatry 2005;29:1062-1073
2. Genecard at NCBI for 5-HTT. XenneX, Inc. 2005 October 18; Retrieved 1/06; Available from URL: http://www.genecards.org/cgi-bin/carddisp?SLC6A4&snpcount=49
3. Serretti A, Kato M, De Ronchi D, Kinoshita T: Meta-analysis of serotonin transporter gene promoter polymorphisms (5-HTTLPR) associated with selective serotonin reuptake inhibitor efficacy in depressed patients. Mol Psych 2007;12:247-257
Method Description Describes how the test is performed and provides a method-specific reference
PCR amplification of the region surrounding the polymorphism followed by size separation of the products.(Lesch KP, Bengel D, Heils A, et al: Association of anxiety-related traits with a polymorphism in the serotonin transporter gene regulatory region. Science 1996;274:1527-1530)
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.
Monday, Thursday; 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 |
|---|---|---|
| 83302 | Serotonin Transporter Genotype | 50330-0 |
| 30133 | Reviewed by | In Process |
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