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AccuType IL28B

AccuType IL28B

Test Highlight

AccuType® IL28B

Clinical Use

  • Predict response to pegylated interferon-α/ribavirin therapy in patients with genotype 1 hepatitis C virus infection

Clinical Background

Chronic hepatitis C virus (HCV) infection affects approximately 4.1 million people in the United States and is the leading cause of cirrhosis, liver cancer, and liver transplantation.1 Recommended HCV treatments, including pegylated interferon-α plus ribavirin, are expensive, poorly tolerated, and ineffective in some people.2 Prediction of treatment response may help clinicians determine an appropriate treatment strategy.3

Both viral and host factors influence the treatment response. For example, HCV genotype is an important viral determinant of response: patients infected with type 1 or 4 have lower sustained virological response (SVR) rates than those infected with type 2 or 3.4 Host factors influencing treatment response include age, gender, ethnicity, and genetic polymorphisms.4,5 For example, European-Americans have higher SVR rates than African-Americans.3,5 Half of this difference is caused by the single nucleotide polymorphism (SNP) IL28B rs12979860.5 This SNP has 3 possible genotypes: CC, CT, and TT. The CC genotype is associated with better rapid virological response (RVR) and SVR rates than are the CT or TT genotypes.3-5 A favorable IL28B genotype improves the treatment response considerably in individuals infected with unfavorable HCV genotypes (1 or 4).3 Individuals infected with HCV genotype 2 or 3 tend to have relatively strong responses irrespective of host factors; a favorable IL28B genotype has less effect in these patients.3 Preliminary studies of HCV-infected liver transplant patients also suggest that the CC (vs CT/TT) genotype in either or in both donor and recipient correlates with higher SVR rates in the recipient.6

The AccuType IL28B test determines the rs12979860 genotype to help predict therapeutic response in HCV-infected patients who are being considered for treatment with pegylated interferon-α/ribavirin.

Method

A real-time PCR allelic discrimination assay is performed on extracted DNA, using fluorescent probes specific for the C and T alleles of the rs12979860 SNP. The SNP genotype (CC, CT, or TT) is reported.

Interpretive Information

Individuals (including liver transplant patients) with the IL28B rs12979860 CC genotype are predisposed to a more favorable treatment response than those with the CT or TT genotypes. Results from this test should be used in conjunction with HCV genotype test results.

The assay detects only C and T alleles of the SNP rs12979860. It does not detect other alleles of this SNP or alleles of other SNPs. Although unlikely, there is a possibility that gene rearrangements may interfere with genotyping.

Additional assistance in interpretation of results is available from our Genetic Counselors by calling 1-866-GENE-INFO (1-866-436-3463).

References

  1. Armstrong GL, Wasley A, Simard EP, et al. The prevalence of hepatitis C virus infection in the United States, 1999 through 2002. Ann Intern Med. 2006;144:705-714.

  2. Ghany MG, Nelson DR, Strader DB, et al. An update on treatment of genotype 1 chronic hepatitis C virus infection: 2011 practice guidelines by the American Association for the Study of Liver Diseases. Hepatology. 2011;54:1433-1444.

  3. Stattermeyer AF, Stauber R, Hofer H, et al. Impact of IL28B genotype on the early and sustained virologic response in treatment-naïve patients with chronic hepatitis C. Clin Gastroenterol Hepatol. 2011;9:344-350.

  4. Sarrazin C, Susser S, Doehring A, et al. Importance of IL28B gene polymorphisms in hepatitis C virus genotype 2 and 3 infected patients. J Hepatol. 2011;54:415-421.

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

  6. McCaughan GW, Shackel NA, Bowen DG. Liver transplantation and hepatitis C: will understanding the interleukin-28B polymorphisms improve outcomes? Liver Transplantation. 2011;17:219-221.

This test was developed and its performance characteristics have been determined by Quest Diagnostics Nichols Institute. Performance characteristics refer to the analytical performance of the test.

Polymerase chain reaction (PCR) is performed pursuant to a license agreement with Roche Molecular Systems, Inc.

Content reviewed 12/2012

 
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