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Interleukin 28B (IL28B) Polymorphism (rs12979860)
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
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.
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.
Whole blood or LabCorp buccal swab kit (buccal swab collection kit contains instructions for use of a buccal swab)
7 mL whole blood or LabCorp buccal swab kit
3 mL whole blood or two buccal swabs
Lavender-top (EDTA) tube, yellow-top (ACD) tube, or LabCorp buccal swab kit
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
|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|