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Tests Conducted on Patients

Tests for hepatitis C virus (HCV) became available in the 1990s. The most common test for HCV is to look for antibodies (anti- HCV) in the blood in response to the infection. Tests detect the amount of viral RNA present or determine the specific subtype of the virus.

A sample of blood is taken from a vein in the arm. This is then subject to the following tests:

  • Anti- HCV test:

    • This detects the presence of antibodies to the virus which indicates exposure to HCV, however, it cannot detect between someone with active or previous HCV infection.

    • The results are usually ‘positive’ or ‘negative’, although there is evidence that if a test is ‘weakly positive’ it could be a false positive.

  • HCV recombinant immunoblot assay (RIBA):

    • This is an additional test which is used to confirm the presence of HCV antibodies.

    • It can tell if the positive anti- HCV test was due to exposure to HCV (positive RIBA) or represents a false signal (negative RIBA).

 

Anti- HCV is not usually detectable in patients with initial signs or symptoms of HCV. It develops in acute infection generally between 2 and 8 weeks after evidence of liver injury. Some may not test positive even after 6-9 months after the onset of illness. The presence of HCV in the bloodstream (viremia) may be detected by RT- PCR within days of contracting the infection. They provide a positive result if present.

 

Most sera containing anti- HCV antibodies are also HCV PCR- positive which suggests that these antibodies are markers of ongoing infection and do not correlate with resolution or eradication of the infection.

 

Figure 4.1 

Example of Polymerase Chain Reaction (PCR) Results 

 

Tests are not yet available to distinguish between acute and chronic HCV infection.

 

Testing Children for Hepatitis C

Children should not be tested for anti- HCV before 12 months of age as anti- HCV from the mother may still be present until this age. Diagnosis relies on determination of ALT (alanine aminotransferase- a liver enzyme) levels and the presence of HCV RNA in baby blood.

  • High levels of ALT indicate liver damage. These enzymes are usually contained within the hepatocytes, but if the liver is damaged then these spill into the blood raising the enzyme level.

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