UDP-Glucuronosyltransferase 1A1 TA Repeat Genotype


Abbrev Code:MMMISC   
Order Code:LAB4909Order Name:Laboratory Miscellaneous Order
Synonyms:Gilbert Syndrome; UGT1A1
Methodology:Real-Time Polymerase Chain Reaction (PCR) with Allelic Discrimination Analysis
CPT Codes: 81350 x1
Turnaround Time:Specimens are sent to reference laboratory Mon-Thur before 1300; results are reported within 3-6 days.
Special Instructions:A completed requisition form must be sent with each sample. A signed informed consent in the patient's medical record is required; the consent should not be sent to the laboratory. See Associated Links.
Associated Links:

Genetic Testing Consent Form


Collection Instructions

Specimen:Blood (see below), Saliva (1 swab in salva collection kit), or Extracted DNA (preferred volume 100 mcl at a concentration of 50 ng/mcl; provide concentration of DNA and volume on 2 mL screw top tube).
Optimal Volume:3 mL whole blood
Minimum\Peds Volume:0.4 mL
Container:Purple (EDTA)
Patient Preparation:Saliva Collection : Patient should not eat, drink, smoke, or chew gum 30 minutes prior to collection.


Processing and Shipping

Specimen Processing:Send specimen in original tube. Do not aliquot.
Shipping Instructions:Ship at room temperature.
Stability:Blood: Ambient (preferred) 9 days/Refrigerated 30 days
Saliva: Ambient 30 days
Extracted DNA: Frozen (preferred)/Ambient/Refrigerated.
Test Performed at or Referral Lab Lab Sendouts  (Mayo Medical Laboratories)
Referral Lab number:U1A1Q


Interpretive

Reference Range:None
Use:
  • Identifying individuals who are at increased risk of adverse drug reactions with drugs that are metabolized by UGT1A1; especially irinotecan but also atazanavir, nilotinib, pazopanib, and belinostat
  • Identifying individuals with Gilbert syndrome due to the presence of homozygous UGT1A1*6 (c.211G>A, based on NM_000463.2) allele, TA7, homozygous TA8, or compound heterozygous *6, TA7 or TA8
  • Identifying individuals who are carriers of Gilbert syndrome due to the presence of heterozygous TA7 or TA8
  • This test is not useful for assessment of Crigler-Najjar syndrome.
 
This pharmacogenomic test interrogates the thymine-adenine (TA) repeat in the TATA-box of the promoter region of UGT1A1. Repeat number may vary from 5 to 8 TA repeats, with 6 TA repeats representing the most common (normal) number of repeats. Individuals with more than 6 TA repeats may have an increased risk for adverse drug reactions to drugs metabolized by UGT1A1, especially atazanavir, irinotecan, nilotinib, pazopanib, and belinostat. Homozygosity for TA7, TA8, or compound heterozygosity for TA7/TA8 is also consistent with a diagnosis of Gilbert syndrome. Heterozygosity for TA7 or TA8 is consistent with carrier status for Gilbert syndrome. Note that this testing uses a tagging single nucleotide variant (SNV) strategy for the TA5 and for the TA7 and TA8 repeats. This testing is not able to distinguish between TA7 and TA8, so both are reported as TA7; however, the function and clinical significance of TA7 and TA8 repeats are thought to be the same. In addition, this test evaluates the UGT1A1*6 (c.211G>A) allele.


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