Coinfection Treatment Issues: Genotyping HCV A viral genotype is a genetic variant of a virus that responds differently to treatment than other variants do. There are at least six genotypes of hepatitis C (HCV), and there are genetic subtypes as well as genotypes. This multiplicity of strains, or "clades," of the HCV virus is not surprising, given its complex pathogenesis and rapid replication rate.
Knowing which genotype of HCV has caused a particular infection can be a decisive factor in prognosis and treatment choice. In the same way that HIV resistance testing is emerging as a key to optimal HIV treatment, HCV genotyping has become a useful tool in the diagnosis of hepatitis and in predicting a person's response to treatments such as interferon.
In one study of over 6000 American patients with chronic hepatitis C, HCV genotype 1 was found in nearly 75%. Patients with either genotype 1 or a pattern of mixed genotypes are also more likely to have higher viral loads, or concentrations of the virus. Although the genotype l pattern creates treatment problems for HCV- and co-infected people nationwide, certain regional and ethnic differences were reported in this study. Significantly more patients from the northeast, southeast, and midwest than from the west or southwest test positive for genotype 1. African Americans were also more likely than caucasians, Hispanics, or Pacific Islanders to have genotype 1 infections.a
Compared with other variants of HCV, genotype 1 is associated with a poorer treatment response and outcome and with more severe liver disease; it is also associated with a higher incidence of liver cancer.b,c
Physicians need to select an appropriate treatment for HCV in coinfected patients with chronic hepatitis, based on HCV genotype and other test results. A review of several studies of adults who had not previously received interferon therapy indicated that combination treatment with ribavirin produced better results than monotherapy with interferon. Patients likely to have a poor response‹such as male patients over 40 with baseline cirrhosis, high viral loads, and HCV genotype 1‹may benefit from combination treatment with alpha interferon and ribavirin for 48 weeks. The presence of genotype 1 alone may indicate the need for this combination regimen. Whichever treatment is selected, careful and consistent monitoring is critical, especially in this higher-risk patient group, since side effects are an important concern.d
references
a. Blatt LM et al. Assessment of hepatitis C virus RNA and genotype from 6807 patients with chronic hepatitis C in the United States. J Viral Hepat. 2000;7(3):.
b. Keeffe EB et al. Utility of hepatitis C virus serotypes in predicting response to treatment of chronic hepatitis C. Cytokines Cell Mol Ther. 1999;5(4):.
c. Zein NN et al. Increased risk of hepatocellular carcinoma in patients infected with hepatitis C genotype 1b. Am J Gastoenterol. 1996;91(12):.
d. Battaglia AM, Hagmeyer. Combination therapy with interferon and ribavirin in the treatment of chronic hepatitis C infection. Ann Pharmacother. 2000;34(4):.
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