Genotyping and Serotyping of HCV

There are six known genotypes and more than 50 subtypes of hepatitis C. The genotype is helpful in defining the epidemiology of hepatitis C. More important, knowing the genotype or serotype (genotype-specific antibodies) of HCV is helpful in making recommendations and counseling regarding therapy. Patients with genotypes 2 and 3 are two to three times more likely to respond to interferon-based therapy than patients with genotype 1. Furthermore, when using combination therapy, the recommended dose and duration of treatment depend on the genotype. For patients with genotypes 2 and 3, a 24-week course of combination treatment using peginterferon and 800 milligrams (mg) of ribavirin daily is adequate, whereas for patients with genotype 1, a 48-week course and full dose of ribavirin (1,000 to 1,200 mg daily) is recommended. For these reasons, testing for HCV genotype is clinically important. Once the genotype is identified, it need not be tested again; genotypes do not change during the course of infection.