UDP Glucuronosyltransferase 1A1 (UGT1A1) Genotyping
Ordering Recommendation

May be useful in dosage planning for individuals who will receive high-dose irinotecan, have a history of irinotecan sensitivity, or experience neutropenia while receiving irinotecan. Confirm suspected diagnosis of Gilbert syndrome.

Polymerase Chain Reaction/Fragment Analysis
Mon, Thu
2-7 days
New York DOH Approval Status
This test is New York DOH approved.
Submit With Order
ARUP Consult®
Disease Topics
Specimen Required
Patient Preparation
Lavender (EDTA), pink (K2EDTA), or yellow (ACD Solution A or B).  
Specimen Preparation
Transport 3 mL whole blood. (Min: 1 mL)  
Storage/Transport Temperature
Unacceptable Conditions
Ambient: 72 hours; Refrigerated: 1 week; Frozen: Unacceptable  
Reference Interval
By report
Interpretive Data
Background Information for UDP Glucuronosyltransferase 1A1 (UGT1A1) Genotyping:
UGT1A1 is responsible for the clearance of drugs (e.g., irinotecan) and endbiotic compounds (e.g., bilirubin). Irinotecan's major active and toxic metabolite (SN-38) is inactivated by the UGT1A1 enzyme and then eliminated via the bile. UGT1A1 gene mutations cause accumulation of SN-38, which may lead to irinotecan-related toxicities (neutropenia, diarrhea).
Variations in TA repeat number in the TATAAA element of the 5' UGT1A1-promoter affects transcription efficiency. The common number of repeats is six [(TA)6, *1 allele], while seven repeats [(TA)7, *28 allele] is associated with reduced transcription activity. Homozygosity for the (TA)7 allele is also associated with Gilbert Syndrome (benign familial hyperbilirubinemia).
Alleles Tested:
*36 allele, (TA)5; *1 allele, (TA)6; *28 allele, (TA)7 and *37 allele, (TA)8.
Clinical Sensitivity/Specificity:
Risk of irinotecan toxicity by genotype (Br J Cancer (2004) 91:678-82).
6/6 (*1/*1): diarrhea 17 percent; neutropenia 15 percent.
6/7 (*1/*28): diarrhea 33 percent; neutropenia 27 percent.
7/7 (*28/*28): diarrhea 70 percent; neutropenia 40 percent.
Allelic Frequency:
*1 (TA)6: Caucasians 0.61, Asians 0.84, African Americans 0.47.
*28 (TA)7: Caucasians 0.39, Asians 0.16, African Americans 0.43.
Polymerase chain reaction followed by size analysis using capillary electrophoresis.
Analytical Sensitivity:
Greater than 99 percent.
Variations in the UGT1A1 gene, other than those targeted, will not be detected. Clinical significance of the rare *36, (TA)5 and *37, (TA)8 alleles in predicting irinotecan toxicities is not well established. Genetic and non-genetic factors other than UGT1A1, may contribute to irinotecan toxicity and efficacy. Diagnostic errors can occur due to rare sequence variations.

Counseling and informed consent are recommended for genetic testing. Consent forms are available online at

Compliance Statement C: The performance characteristics of this test were validated by ARUP Laboratories. The U.S. Food and Drug Administration (FDA) has not approved or cleared this test; however, FDA approval or clearance is currently not required for clinical use of this test. The results are not intended to be used as the sole means for clinical diagnosis or patient management decisions. ARUP is authorized under Clinical Laboratory Improvement Amendments (CLIA) and by all states to perform high-complexity testing.

Counseling and informed consent are recommended for genetic testing. Consent forms are available online.
CPT Code(s)
Component Test Code*Component Chart NameLOINC
0051333UGT1A1 Genotyping Allele 151951-2
0051334UGT1A1 Genotyping Allele 251952-0
0051335UGT1A1 Genotyping Interpretation50398-7
2001384UGT1A1 Genotyping Specimen31208-2
* Component test codes cannot be used to order tests. The information provided here is not sufficient for interface builds; for a complete test mix, please click the sidebar link to access the Interface Map.
  • Irinotecan Toxiicity
  • UGT1A1