Why are there two tests?

Two tests need to be done to discover if you have hepatitis C.

The antibody test

A hepatitis C antibody test is the first test undertaken. This is to determine whether you have ever been exposed to the hepatitis C virus. It works by testing for the presence of antibodies to the virus generated by your immune system. If you receive a negative hepatitis C antibody test but have been experiencing symptoms or have been recently exposed to hepatitis C, then you are likely to be advised to have a second test.

It is important to remember that there is a 'window period'. This is the short period of time when your immune system may not have had time to produce antibodies. It usually takes between six and twelve weeks for these antibodies to develop. However, in a few people it can take up to six months. So if you have the test within this window period and the result is negative, it does not necessarily mean that you don't have the virus.

If you receive a positive hepatitis C antibody test it does not necessarily mean you are currently infected. Up to 20% of people clear the virus from their bodies naturally. This is called ‘spontaneous clearance’. Although they have cleared the virus, tests will still show the presence of hepatitis C antibodies. There is a chance that you may have been infected with hepatitis C in the past but you are no longer infected.

The PCR test

If an antibody test is positive, a second test will check if the virus is still present. Both tests are able to be done from one sample from you so it does not always mean that you have to get tested twice. However, some testing services still only test for the presence of antibodies first and then call you back for a further PCR test.

The PCR (polymerase chain reaction) test determines whether you are currently infected by detecting the presence of the genetic material of the virus in the blood. This genetic material is called RNA and this test is sometimes referred to as an RNA test.

Test results are generally reported as either ‘undetectable’ or ‘detectable’. Positive results are often given in terms of the amount of virus found in a unit of blood. This is called the viral load.

You should be given the results of both your antibody test and your PCR test at the same time. That way you immediately know whether you are currently infected and need to be referred to a specialist.

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