is used to determine the kind, or genotype, of the virus
present. There are 6 major types of HCV; the most common (genotype 1) is
less likely to respond to treatment than genotypes 2 or 3 and usually
requires longer therapy (48 weeks, versus 24 weeks for genotype 2 or 3).
Genotyping is often ordered before treatment is started to give an idea
of the likelihood of success and how long treatment may be needed.