Mayo Test Catalog, (Sorted By Test Name) - Mayo Medical ...

HTR2
83303
with earlier dating. Babies with trisomy 18 tend to be small, which can lead to underestimation of
gestational age and an increased risk of missing a true-positive. When both Sequential Maternal Screening
Part 1 and Part 2 of sequential screening are performed with a screen cutoff of 1/100, the combination of
maternal age, PAPP-A, AFP, uE3, and hCG, has an overall detection rate of approximately 90% with a
false-positive rate of approximately 0.1%. Follow-up: Verify that all information used in the risk
calculation is correct (maternal date of birth, gestational dating, etc). If any information is erroneous,
contact the laboratory for a revision. Screen-negative results typically do not warrant further evaluation. If
the results are positive, the patient is typically offered counseling, ultrasound, diagnostic testing, and,
possibly, a referral to genetics counseling or a high-risk clinic.
Reference Values:
An interpretive report will be provided. See Interpretation section for more details.
Clinical References: 1. Malone FD, Canick JA, Ball RH, et al: First-trimester or second-trimester
screening, or both, for Down's syndrome. N Engl J Med 2005 Nov 10;353(19):2001-2011 2. Screening
for fetal chromosomal abnormalities. ACOG Practice Bulletin No. 77. American College of
Obstetricians and Gynecologists. Obstet Gynecol 2007;109:217-227 3. Wald NJ, Rodeck C, Hackshaw
AK, et al: SURUSS in Perspective. Semin Perinatol 2005;29:225-235 4. Palomaki GE, Steinort K,
Knight GJ, et al: Comparing three screening strategies for combining first- and second-trimester Down
syndrome markers. Obstet Gynecol 2006 Feb;107(2 Pt 1): 367-375 5. Palomaki GE, Neveux LM,
Knight GJ, et al: Maternal serum-integrated screening for trisomy 18 using both first- and
second-trimester markers. Prenat Diagn 2003 Mar;23(3):243-247
Serotonin Receptor Genotype (HTR2A and HTR2C)
Clinical Information: 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
Useful For: 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
Interpretation: An interpretive report will be provided.
Reference Values:
An interpretive report will be provided.
Clinical References: 1. Kato M, Serretti A: Review and meta-analysis of antidepressant
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