There are many different tests performed on people who are suspected of having hepatitis C infection or in whom hepatitis C is diagnosed. These are to help in diagnosis, or to follow its progression, or to see the response to treatment.
Blood tests
Hepatitis C antibodies are detected by a blood test known as an anti-HCV test. It looks for antibodies to hepatitis C which are produced by the body’s immune system in response to the virus. This test does not detect the virus itself, but rather the body’s immune response to the virus.
A positive antibody test will usually be confirmed on the same sample by a second antibody test and then by a later test on another sample of blood.
A positive result, known as anti-HCV positive, shows that a person has been exposed to the virus at some time. It does not detect whether the virus is still present or whether the person is infectious.
It may take a long time, sometimes a few months, for antibodies to appear in blood following infection. It is usually eight to twelve weeks after exposure to the virus, but can occasionally be up to six months or more; this means that an antibody test taken too early may not detect exposure to hepatitis C.
The hepatitis C virus itself can be detected by a molecular test called Polymerase Chain Reaction (PCR). This test is normally done only in people who are anti-HCV positive. If the PCR test is positive, the individual is infected.
Liver function test (LFTs)
Liver function tests (LFTs) are blood tests that measure substances in the bloodstream which indicate that the liver is damaged. However, they are not always good indicators of liver damage and do not detect the presence of the virus. LFT levels can fluctuate throughout the course of the disease. Sometimes they are normal, but this does not prove that liver damage is absent.
Liver biopsy
The only way to assess the amount of liver damage is a liver biopsy which involves taking a small sample of liver tissue for examination under a microscope. The test is usually performed under a local anaesthetic. A hollow fine needle is passed through the skin into the liver and a small piece of tissue is withdrawn inside the needle.
In most people the procedure can be uncomfortable, so good pain relief is important, though in some cases the procedure is quite painless. In many hospitals the procedure is performed as a day case, in others an overnight stay is necessary. The results of the biopsy are graded and staged according to the degree of inflammation and scarring.
Following a biopsy, some people feel sore and/or experience some discomfort. Therefore, anyone having a biopsy should think about making arrangements for someone to collect them from the hospital and to take them home.
Strains of hepatitis C
The hepatitis C virus is not a single type of virus. There are different strains (genotypes) of hepatitis C with numerous subtypes.
Different strains vary from country to country. In the UK, Western Europe and the United States the most common strains are types 1, 2 and 3. Subtypes are labelled a, b, c, etc. Therefore the patient could have hepatitis C 1a, hepatitis C 2a or hepatitis C 2b, and so on.
It is possible to be infected again with a different strain, or be infected with two strains at the same time. The different strains do not appear to result in different patterns of disease, but they do differ in their response to treatment.
Because treatment response does vary according to the strain of hepatitis C infection, a test is usually performed to determine the strain before treatment is advised. Genotype 1 is the most difficult strain to treat with current therapy.
The results of the various tests can be confusing and require specialist interpretation. It is important that people who have hepatitis C are referred to a specialist who should be a hepatologist or a gastroenterologist with knowledge of liver disease.
