Laboratory diagnosis is most important to establish the specific diagnosis of hepatitis caused by HCV.
Hepatitis C infection can be confirmed by employing serologi-cal tests to detect antibodies to HCV. Antibodies are directed against core envelope and NS3 and NS4 proteins and tend to be relatively low in titer. Acute HCV antibodies are usually demonstrated in acute infections 6–8 weeks after initial infec-tion. Then antibodies that are produced persist throughout life in chronic infection.
ELISAs, including second- and third-generation ELISAs, are useful for screening of serum for anti-HCV antibodies. These assays are highly specific but cannot differentiate acute infec-tion from chronic infection. The ELISA which employs anti-bodies against core proteins and nonstructural proteins 3, 4, and 5 is the most recent third-generation enzyme immunoas-say (EIA). The test can detect antibodies in the serum 8 weeks after the onset of infection. Recombinant immunoblot assay using recombinant HCV antigen is a highly specific test to detect HCV infection. This test, which is more specific than the ELISA, has been used to confirm positive ELISA results.