Hepatitis C Virus (HCV) Antibody

• Has been exposed to someone with HCV
• Participates in high risk behaviors such as injecting street drugs
• Has abnormal liver function tests
• Has symptoms associated with liver disease, such as jaundice, dark urine, nausea, or unexpected weight gain or loss

The following tests may be used to screen for and/or detect HCV:

• Anti-HCV test detects the presence of antibodies to the virus, indicating exposure to HCV. This test cannot distinguish between someone with an active or a previous HCV infection. Usually, the test is reported as "positive" or "negative." There is some evidence that if the test is "weakly positive," it may be a false positive. The Centers for Disease Control and Prevention (CDC) suggests that weakly positive tests be confirmed with the HCV RIBA test before being reported.
• HCV recombinant immunoblot assay (RIBA) test is an additional test ordered to confirm the presence of HCV antibodies. In most cases, it can tell if the positive anti-HCV test was due to exposure to HCV (positive RIBA) or represents a false signal (negative RIBA). In a few cases, the results cannot answer this question (indeterminate RIBA). Like the anti-HCV test, the RIBA test cannot distinguish between a current or past infection.

The following tests may be used to diagnose a current infection and to guide and monitor treatment:

• HCV RNA test, Qualitative may be used to distinguish between a current or past infection. It is reported as a "positive" or "detected" if any HCV viral RNA is found; otherwise, the report will be "negative" or not detected." It may also be ordered after HCV treatment is complete to see if the virus has been eliminated from the blood. These tests are seldom used any more.
• HCV Viral Load (HCV RNA test, Quantitative) detects and measures the number of viral RNA particles in the blood. Viral load tests are often used before and during treatment to help determine response to treatment by comparing the amount of virus before and during treatment (usually at several time points in the first three months of treatment). Successful treatment causes a decrease of 99% or more (2 logs) in viral load soon after starting treatment (as early as 4-12 weeks) and usually leads to viral load being not detected even after treatment is completed. Some newer viral load tests can detect very low amounts of viral RNA.
• Viral genotyping is used to determine the kind, or genotype, of the HCV 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.