Test code links throughout this Guide refer to the corresponding test in the User's Guide. HCV RNA is extracted from serum or plasma using guanidinium thiocyanate. HCV is a 9.5 Kb single-strand RNA virus that has been classified as a separate genus in the family Flaviviridae . A high spontaneous mutation frequency has produced an extremely heterogeneous group of clinically relevant subtypes. The development of antibody screening tests has lead to a dramatic decrease in post-transfusion HCV infection.
Most patients remain chronically infected.
Interferons have been used to treat chronic HCV infection. Most clinical experience has been with interferon alpha-2b, which in randomized trials has been shown to significantly benefit certain patients. Combination therapy with interferon and the antiviral agent Ribavirin is being studied and may prove to be more effective. Nucleic acid sequencing has led to the identification of 6 common HCV types and many more subtypes depending on the system of classification. The clinical course of infection and the responsiveness to alpha interferon correlate with viral type.