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HelpTest ID OIL28 Interleukin 28B (IL28B) Polymorphism (rs12979860), Saliva
Useful For
Predicting responsiveness of genotype 1 hepatitis C viral infections to combined pegylated-interferon and ribavirin-based therapies
Genotyping patients who prefer not to have venipuncture done
Special Instructions
Method Name
Polymerase Chain Reaction (PCR) Followed by 5'-Nuclease End-Point Allelic Discrimination Analysis
(PCR is utilized pursuant to a license agreement with Roche Molecular Systems, Inc.)
Reporting Name
IL28B Polymorphism Genotype, SalivaSpecimen Type
SalivaMultiple saliva genotype tests can be performed on a single specimen after a single extraction. See Multiple Saliva Genotype Tests in Special Instructions for a list of tests that can be ordered together.
Container/Tube: Oragene DNA Self-Collection Kit (T651: fees apply)
Specimen Volume: Full tube
Collection Instructions:
1. Fill tube to line.
2. Send specimen in original container per kit instructions.
Forms: 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 (Supply T576) is available in Special Instructions.
Specimen Minimum Volume
1 mL
Specimen Stability Information
| Specimen Type | Temperature | Time |
|---|---|---|
| Saliva | Ambient | |
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.
Reference Values
An interpretive report will be provided
Cautions
This test does not detect variants other than the single-nucleotide variant of rs12979860 CT.
Drug-drug interactions and drug-metabolite inhibition must be considered.
IL28B is expressed in the liver following hepatitis C virus infection. For liver transplant patients, the IL28B genotype of the recipient and the donor are independent predictors of sustained virologic response with combined pegylated-interferon and ribavirin therapy.(4)
Rare variants exist and could lead to false-negative or false-positive results.
Day(s) Performed
Friday; 9 a.m.
Report Available
1 day (not reported on Saturday or Sunday)Performing Laboratory
Mayo Medical Laboratories in Rochester
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