Hepatitis C

What is being analysed?
The hepatitis C virus is a virus that can infect and damage the liver. In most cases it is caught through exposure to blood (usually by sharing contaminated needles when injecting drugs or, before 1992, through blood transfusions) or through sexual intercourse, and it can be passed from mother to baby. There are also less common, but possible, routes of transmission. Antibodies against hepatitis C are produced in response to exposure to the hepatitis C virus (HCV). The most common test for HCV looks for these antibodies in the blood. Other tests detect the presence of viral RNA, measure the amount of viral RNA present, or determine the specific subtype of the virus

How is it used?
When is it requested?
What does the test result mean?
Is there anything else I should know?

How is it used?
Each of the five most common tests has a slightly different purpose:

• Anti-HCV tests detect antibodies against the virus, which indicate
exposure to HCV. These tests cannot tell whether you still have an active viral infection, only that you have been exposed to the virus in the past. The test usually has two possible results: “positive” or “negative”. There is some evidence that a “weakly positive” result may not mean past exposure to the virus. The Centers for Disease Control and Prevention (CDC) revised its guidelines in 2003 and suggests that a weakly positive result be confirmed with a further test before being reported.

• The HCV RIBA test is an additional test to confirm the presence of antibodies against the virus. In most cases it can tell whether a positive anti-HCV was due to exposure to HCV (RIBA positive) or is a false signal (RIBA negative). In a few cases the results cannot settle the question (RIBA indeterminate). Like anti-HCV, the RIBA test does not show an active infection, only whether you have been exposed to the virus.

• The HCV RNA test shows whether the virus is circulating in the blood, indicating an active HCV infection. In the past it was usually done as a test called qualitative HCV. Qualitative HCV RNA can be “positive” or “detected” if HCV RNA is found; otherwise the test will be “negative” or “not detected”. The test can also be used to see whether treatment has eliminated the virus from the body.

• Viral load or quantitative HCV measures the number of virus particles in the blood. These tests are often used before and during treatment to help understand the response to treatment by comparing the amount of virus before and after treatment (usually after three months); treatment can be considered effective if it produces a fall of 99% or more in viral load soon after starting (within 4-12 weeks), and it generally leads to an undetectable viral load. Some newer viral load tests can detect very small amounts of virus, and some
laboratories no longer perform qualitative HCV RNA testing if they use these newer tests.

• Viral genotyping is used to determine the type, or genotype, of the virus present. There are 6 main types of HCV; the most common (genotype 1) responds less well to treatment than genotypes 2 or 3 and usually needs longer treatment (48 weeks, compared with 24 weeks for genotypes 2 or 3). Genotyping is often requested before treatment starts to give an idea of how likely it is to succeed and how long it should last.

When is it requested?
Hepatitis C is the most common cause of chronic liver disease in North America; about 2% of all adults in the United States have been exposed to the virus, and 75-85% of these are chronically infected. The CDC recommends HCV testing in the following cases:

• If you have ever used illegal drugs
• If you had blood transfusions or an organ transplant before July 1992*
• If you received clotting factors produced before 1987
• If you are on long-term dialysis
• For children born to HCV-positive women
• For healthcare workers who have had a needlestick injury, a cut or mucosal exposure to HCV-positive blood.
• For people with clinically evident chronic hepatitis

*The blood supply has been screened in the US since 1990, and every unit of blood positive for HCV has been discarded. The current risk of HCV infection from transfused blood is about 1 case per 2 million units transfused.

A positive anti-HCV test can be confirmed with the HCV RIBA test, especially if it is “weakly positive”. Qualitative HCV RNA is often used when the antibody test is positive to check whether the infection is still present. HCV viral load and genotyping may be carried out to plan treatment; viral load and qualitative HCV RNA are also used to monitor the response to treatment.

What does the test result mean?
If the antibody test is positive, there has probably been an infection with hepatitis C virus, even if the symptoms were so mild that you do not remember them.

A positive RIBA confirms exposure to the virus, while a negative RIBA indicates that the first test was probably a false positive, i.e. there has never been an HCV infection.

A positive (or detectable) HCV RNA points to an active HCV infection.

Is there anything else I should know?
Anti-HCV antibodies usually do not appear for several months after infection, but persist in the later stages of the disease.

1. If the disease is very mild, why should I have the test?
2. Are there other tests to follow the disease?
3. Is there a vaccine for HCV?
4. Is there a treatment for HCV?
5. Can I do the test at home?
6. How can I tell others that I am infectious?

1. If the disease is very mild, why should I have the test?
Hepatitis C often leads to chronic hepatitis, which can progress to cirrhosis and liver cancer (hepatocellular carcinoma). Early detection of the virus can prompt your doctor to monitor your liver function more closely and consider treatment if there is a chronic infection.

2. Are there other tests to follow the disease?
Yes. Liver tests such as ALT and AST show liver damage. People who remain infected with HCV but have normal ALT and AST probably have less severe liver disease and may not need treatment. Other liver tests that can be used are albumin, prothrombin time and bilirubin; these are usually normal until cirrhosis develops. Sometimes a liver biopsy is needed to determine how severe the liver damage is.

3. Is there a vaccine for HCV?
No. There is currently no vaccine available. Producing one is difficult because the virus has several different molecular forms that are constantly changing.

4. Is there a treatment for HCV?
Yes, there are currently several medicines that can be used to treat HCV infection. A combination of two medicines (interferon and ribavirin) is mainly used. New medicines are currently being studied. Depending on age, sex, HCV viral load and the extent of liver damage, the chance of successful treatment ranges from very low to over 80%.