HEPATITIS C SEROLOGY

INTERPRETING HEPATITIS C SEROLOGY

Hepatitis C liver disease caused by the hepatitis C virus (HCV) can be acute or chronic. Although most people with newly acquired hepatitis C infection will have no obvious symptoms, up to 85% will go on to have a chronic infection. Those that spontaneously clear the virus on their own are said to have resolved the infection. Since anti-viral treatment is intended for people with current hepatitis C infection, it is important to distinguish those with chronic infection from those whose infection is resolved.

+Hepatitis C antibody (Anti-HCV) test

The first stage is a hepatitis C antibody (Anti-HCV) test. When the hepatitis C virus enters a person’s bloodstream, it triggers an immune response and makes antibodies to the virus. Antibodies to hepatitis C can be detected in the blood, usually within two or three months but sometimes up to six months or more after exposure to the virus. The Anti-HCV test detects the presence of antibodies to the hepatitis C virus. Using an enzyme immunoassay (EIA) or similar testing technologies, Anti-HCV antibodies are detectable in the vast majority of people with hepatitis C infection.

Anti HCV Negative (non-reactive)

If the anti-HCV test is negative it usually means that the person has not been infected with hepatitis C. However, results may be negative in early acute hepatitis C and during the ‘window period’ or in people with weakened immune systems. In these situations, and where a person has been exposed to risk of infection during the window period, ongoing monitoring and follow up testing should always be offered.

People with suppressed or weakened immune systems, including those with HIV, or those receiving certain medications including immunosuppressant drugs, are not always able to produce antibodies.

HCV antibody positive (reactive)

A positive hepatitis C antibody test means that the person has, at some time, been exposed to the hepatitis C virus. It does not necessarily mean a person is currently infected and a confirmatory test will be needed to determine if the person is currently infected or not. After infection, the hepatitis C antibodies stay in the blood permanently, even if the virus is no longer present.

All people with a positive HCV antibody test should have a confirmatory HCV RNA test to determine the presence of active infection. It is recommended that the confirmatory test should be taken from the same sample (either through venapuncture or dried blood spot testing (DBS) is used for the antibody test.

Roughly one in five people who are infected with hepatitis C spontaneously clear the virus completely without needing any treatment. However, it is important to note that even if someone has previously cleared the virus any future exposure to the virus could cause infection – having hepatitis C antibodies does not give immunity against reinfection.

+Confirmatory (HCV RNA) test

The second stage is a confirmatory (HCV RNA) test. Both venipuncture or DBS samples that are positive for hepatitis C antibody should automatically be tested for the presence of the hepatitis C virus. Samples should be of sufficient quantity to allow for this and prevent the need for additional sampling.

Using nucleic acid tests (NAT) or antigen techniques, the HCV RNA test will detect the presence or absence of virus. Usually using a subset of the specimen used for Anti-HCV testing, the PCR tests looks for genetic material – ribonucleic acid – of the hepatitis C virus (HCV RNA).

This test will be reported as either negative (no virus present) or positive (virus present) confirming the person has hepatitis C infection and at risk of developing serious liver disease.

+Antigen test –
HCV Core Antigen as a serologic marker

HCV antigen testing also has the potential to reduce the cost of diagnostic testing, and of treatment monitoring and could eventually replace the current two-step procedure for diagnosing chronic hepatitis C infection in lower- and middle-income countries, speeding up access to treatment and improving retention in care.

EASL Guidelines on the Treatment of Hepatitis C recommend that although core antigen assays are slightly less sensitive than HCV RNA assays for detection of viral replication, HCV core antigen tests should be used if HCV RNA assays are not available or not affordable to identify patients with on-going infection.