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Test ID: HTT Serotonin Transporter Genotype, Blood

Reporting Name

Serotonin Transporter Genotype

Useful For

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

Specimen Type

Whole Blood EDTA


Specimen Required


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


Specimen Minimum Volume

0.3 mL

Specimen Stability Information

Specimen Type Temperature Time
Whole Blood EDTA Ambient (preferred)
  Refrigerated 

Reference Values

An interpretive report will be provided.

Day(s) and Time(s) Performed

Monday, Thursday; 8 a.m.

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

81479 -Unlisted molecular pathology procedure

LOINC Code Information

Test ID Test Order Name Order LOINC Value
HTT Serotonin Transporter Genotype 50330-0

 

Result ID Test Result Name Result LOINC Value
83302 Serotonin Transporter Genotype 50330-0
30133 Reviewed by No LOINC Needed

Clinical Information

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.

Interpretation

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.

 

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.

Clinical Reference

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 at 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

Analytic Time

1 day (not reported Saturday or Sunday)

Method Name

Polymerase Chain Reaction (PCR) Followed by Sizing Analysis

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 (T576) is available in Special Instructions.

Mayo Medical Laboratories | Genetics and Pharmacogenomics Catalog Additional Information:

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