Interleukin 28B (IL28B) Polymorphism (rs12979860)

CPT: 81283
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Test Details

Use

Genome-wide association studies have identified a single nucleotide polymorphism (SNP) (rs12979860) upstream of the IL28B gene, which is associated with higher sustained viral response rates to pegylated interferon/ribavirin therapy in HCV genotype 1-infected individuals. The CC genotype, as compared to either the CT or TT genotypes, has been associated with an approximately twofold to threefold greater rate of sustained viral response in hepatitis C virus genotype 1 chronically-infected individuals treated with combination pegylated interferon/ribavirin therapy.1 Similar sustained viral response associations across various racial groups including European Americans (95% CI 1.8−2.3), African Americans (95% CI 1.9−4.7), and Hispanics (95% CI 1.4−3.2) have been observed.1 The CC genotype has also been associated with a threefold increase in rate of spontaneous clearance of HCV.2 Allele frequencies for the rs12979860 C allele vary across racial and ethnic groups. The rs12979860 C variant is most frequently present in individuals from East Asia (allele frequency >0.9) and least common in individuals of African origin (allele frequency 0.2−0.5).2 In a recent US-based study, the favorable CC genotype was observed in 37% of Caucasians, 29% of Hispanics, and 14% of African Americans tested.3

Limitations

IL28B genotype is only one of many factors that can influence response rates to pegylated interferon/ribavirin therapy in HCV genotype 1 infection and should be interpreted in the context of other clinical factors. The mechanism by which the IL28B genotype mediates pegylated interferon/ribavirin treatment response in HCV genotype 1 is not yet understood and is the subject of intense research. The impact of the IL28B polymorphism on response rates in HCV genotypes other than genotype 1 is still being investigated.

Methodology

Real-time polymerase chain reaction (PCR) with allele-specific TaqMan® probes is used to detect a single nucleotide polymorphism (SNP) (rs12979860 C/T) on chromosome 19q13. The rs12979860 SNP maps 3 kilobases upstream of the IL28B gene (OMIM 607402), which encodes the type III interferon-λ3. No other polymorphisms are detected by this assay.

Specimen Requirements

Specimen

Whole blood or LabCorp buccal swab kit (buccal swab collection kit contains instructions for use of a buccal swab)

Volume

7 mL whole blood or LabCorp buccal swab kit

Minimum Volume

3 mL whole blood or two buccal swabs

Container

Lavender-top (EDTA) tube, yellow-top (ACD) tube, or LabCorp buccal swab kit

Storage Instructions

Maintain specimen at room temperature or refrigerate at 4°C.

Causes for Rejection

Frozen specimen; hemolysis; quantity not sufficient; improper container; one buccal swab; wet buccal swab

Clinical Information

Footnotes

1. Ge D, Fellay J, Thompson AJ, et al. Genetic variation in IL28B predicts hepatitis C treatment-induced viral clearance. Nature. 2009 Sep 17; 461(7262):399-401. 19684573
2. Thomas DL, Thio CL, Martin MP, et al. Genetic variation in IL28B and spontaneous clearance of hepatitis C virus. Nature. 2009 Oct 8; 461(7265):798-801. 19759533
3. Thompson AJ, Muir AJ, Sulkowski MS, et al. Interleukin-28B polymorphism improves viral kinetics and is the strongest pretreatment predictor of sustained virologic response in genotype 1 hepatitis C virus. Gastroenterology. 2010 Jul; 139(1):120-129. 20399780

LOINC® Map

Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
480630 IL28B Polymorphism Genotype 480631 IL28B Polymorphism Result: 60279-7
480630 IL28B Polymorphism Genotype 480633 Interpretation: 77202-0
480630 IL28B Polymorphism Genotype 480634 Additional Information: 77202-0
480630 IL28B Polymorphism Genotype 480638 Methodology: 49549-9
480630 IL28B Polymorphism Genotype 480636 References: 75608-0
480630 IL28B Polymorphism Genotype 480637 Director Review: 72486-4

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The LOINC® codes are copyright © 1994-2018, Regenstrief Institute, Inc. and the Logical Observation Identifiers Names and Codes (LOINC) Committee. Permission is granted in perpetuity, without payment of license fees or royalties, to use, copy, or distribute the LOINC® codes for any commercial or non-commercial purpose, subject to the terms under the license agreement found at https://loinc.org/license/. Additional information regarding LOINC® codes can be found at LOINC.org, including the LOINC Manual, which can be downloaded at LOINC.org/downloads/files/LOINCManual.pdf