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Test ID: BIL28 Interleukin 28B (IL28B) Polymorphism (rs12979860), Blood

Reporting Name

IL28B Polymorphism Genotype, B

Useful For

Predicting responsiveness of genotype 1 hepatitis C viral infections to combined pegylated-interferon and ribavirin-based therapies in whole blood specimens

Specimen Type

Whole Blood EDTA

Specimen Required

Multiple whole blood EDTA genotype tests can be performed on a single specimen after a single extraction. See Multiple Whole Blood EDTA Genotype Tests in Special Instructions for a list of tests that can be ordered together.


Container/Tube: Lavender top (EDTA)

Specimen Volume: 3 mL

Collection Instructions: Send specimen in original tube.

Specimen Stability Information

Specimen Type Temperature Time
Whole Blood EDTA Ambient (preferred)

Reference Values

An interpretive report will be provided.

Day(s) and Time(s) Performed

Tuesday; 9 a.m.

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information

81400-IL28B (interleukin 28B [interferon, lambda 3]) (eg, drug response), rs12979860 variant

LOINC Code Information

Test ID Test Order Name Order LOINC Value
BIL28 IL28B Polymorphism Genotype, B 60279-7


Result ID Test Result Name Result LOINC Value
34627 IL28B Polymorphism Genotype 60279-7
34628 IL28B Interpretation 69047-9
34629 Reviewed by No LOINC Needed

Clinical Information

Individuals with hepatitis C virus (HCV) genotype 1 infections have variable responses to treatment with pegylated-interferon and ribavirin combination therapy. Some individuals will respond to treatment with sustained viral response, while other patients have poor response and fail to achieve sustained viral clearance.


Response to pegylated-interferon and ribavirin combination therapy in HCV genotype 1-infected individuals has been found to be closely associated with a single-nucleotide polymorphism (SNP), designated rs12979860, located 3 kilobases upstream from the interleukin 28B gene locus (IL28B) present on human chromosome 19.


HCV genotype 1-infected individuals with the CC genotype, as compared to either the CT or TT genotypes, of this SNP in IL28B have approximately 2- to 3-fold greater rates of sustained viral response to combined pegylated-interferon and ribavirin therapy.(1) Similar increases in sustained viral response rates were observed across various racial groups, including European Americans (95% CI, 1.8- to 2.3-fold), African Americans (95% CI, 1.9- to 4.7-fold), and Hispanics (95% CI, 1.4- to 3.2-fold).(1) The CC genotype has also been associated with a 3-fold increase in rate of spontaneous clearance of HCV.(2) The SNP in IL28B is only one of many factors that can influence response rates to pegylated-interferon and ribavirin combination therapy in HCV genotype 1 infection, and the SNP genotype result should be interpreted in the context of other clinical factors present in a given patient.


Frequency of the rs12979860 C allele varies across different 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% Hispanics, and 14% of African Americans tested.


The mechanism by which the IL28B genotype mediates response to pegylated-interferon and ribavirin combination therapy among HCV genotype 1-infected individuals is not yet understood and is the subject of intense ongoing research. The impact of the IL28B-related polymorphism on response rates in patients infected with HCV genotypes other than genotype 1 is still being investigated.


An interpretative report will be provided.

Clinical Reference

1. Ge D, Fellay J, Thompson AJ, et al: Genetic variation in IL28B predicts hepatitis C treatment-induced viral clearance. Nature 2009;461:399-401

2. Thomas DL, Thio CL, Martin MP, et al: Genetic variation in IL28B and spontaneous clearance of hepatitis C virus. Nature 2009;461:798-801

3. Chalton MR, Thompson A, Veldt BJ, et al: Interleukin-28B polymorphisms are associated with histological recurrence and treatment response following liver transplantation in patients with hepatitis C virus infection. Hepatology 2011;53:317-324

4. Thompson AJ, Muir AJ, Sulkowski MS, et al: Interleukin-28B polymorphism improves viral kinetics and is the strongest pre-treatment predictor of sustained virologic response in hepatitis C virus-1 patients. Gastroenterology 2010;139:120-129

Analytic Time

1 day (not reported on Saturday or Sunday)

Method Name

Polymerase Chain Reaction (PCR) Followed by 5’-Nuclease End-Point Allelic Discrimination Analysis

Specimen Minimum Volume

0.3 mL


New York Clients-Informed consent is required. Please document on the request form or electronic order that a copy is on file. An Informed Consent for Genetic Testing (T576) is available in Special Instructions.

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