How is hepatitis C diagnosed?

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A blood test can detect antibodies in your blood to hepatitis C. (Antibodies are proteins made by the immune system to attack viruses, bacteria, etc. The specific antibody against hepatitis C can be detected by a simple routine blood test.) A positive test means that you have at some stage been infected with hepatitis C.

However, this test remains positive even in people who have cleared the virus from their body. (The antibodies remain even if the virus has gone.) Also, it can take up to six months for the antibody test to become positive after first being being infected. (As the body may take a while to make these antibodies.) So, a negative test does not necessarily rule out a recently acquired infection. A repeat test in a few weeks may be advised in some people who have recently been at risk of catching hepatitis C.

If the antibody test is positive, then a further blood test is needed to see if the virus is still present (chronic infection). This is a more specialised test which detects particles of the virus. Also, there are several different strains (types) of the hepatitis C virus. Tests may be done to find exactly which strain you are infected with. Some strains are more resistant to treatment than others.

Assessing the severity of the infection?

If you are found to have virus present, then other tests may be advised to check on the extent of inflammation or damage to the liver. For example:

Blood tests called liver function tests are commonly done. These measure the activity of enzymes (chemicals), proteins and other substances made in the liver. See separate leaflet called 'Liver Function Tests'.
A biopsy (small sample) of the liver may be taken to look at under the microscope. This can show the extent of any inflammation, scarring, cirrhosis, etc, in the liver.
Other tests may be done if cirrhosis or other complications develop.