BOX 2-5

CDC Hepatitis C Virus Infection Case Definition (Past or Present)

Clinical description:

Most HCV-infected persons are asymptomatic. However, many have chronic liver disease, which can range from mild to severe including cirrhosis and liver cancer.

Laboratory criteria for diagnosis:

  • Anti-HCV positive (repeat reactive) by EIA, verified by an additional more specific assay (e.g., RIBA for anti-HCV or nucleic acid testing for HCV RNA),


  • HCV RIBA positive,


  • Nucleic acid test for HCV RNA positive,


  • Report of HCV genotype,


  • Anti-HCV screening-test-positive with a signal to cut-off ratio predictive of a true positive as determined for the particular assay (e.g., 3.8 for the enzyme immunoassays) as determined and posted by CDC.

Case classification:

Confirmed: a case that is laboratory confirmed and that does not meet the case definition for acute hepatitis C.

Probable: a case that is anti-HCV positive (repeat reactive) by EIA and has ALT or SGPT values above the upper limit of normal, but the anti-HCV EIA result has not been verified by an additional more specific assay or the signal to cutoff ratio is unknown.

Abbreviations: CDC, Centers for Disease Control and Prevention; HCV, hepatitis C virus; EIA, enzyme immunoassay; RIBA, recombinant immunoblot assay; RNA, ribonucleic acid; ALT or SGPT, alanine aminotranferase.

SOURCE: CDC, 2009a.

zyme immunoassay (EIA). A repeatedly reactive EIA is followed by a more specific assay to detect viremia, such as the recombinant immunoblot assay (RIBA) for anti-HCV, or by nucleic acid testing for HCV RNA. In some cases, an EIA with a high signal-to-cutoff ratio predictive of a true positive will be used in the place of a confirmatory RIBA. However, all confirmed anti-HCV test results should be followed by a test for the presence of HCV

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