How reliable is the result of such a test? | Test for Hepatitis B

How reliable is the result of such a test?

The test methods used today are very safe and have high sensitivity (describes ability to identify sick people as sick) and specificity (describes ability to identify healthy people as healthy). In almost all cases the test results are therefore safe. However, the variable incubation time of hepatitis B poses a problem for test safety. Only after about three months can one actually assume that no infection has occurred if the test is negative.

From when can you do such a test after exposure?

In principle, the test can be performed immediately after exposure, but then only shows the status quo before the infection event in question. It makes sense to perform the test a few weeks after exposure. The viral DNA may be detectable as early as one week after contact, the various virus components only 2-4 weeks later. It is generally assumed that a test for hepatitis B would be positive after about three months if an infection has occurred.

Is it possible to do such a test during pregnancy?

Not only can a hepatitis B test be taken during pregnancy, it is even routinely performed on pregnant women. However, not all the above-mentioned virus components and antibodies are tested, but only HBsAg, the surface protein of the hepatitis B virus. It is elevated during active infection and is tested in the last third of pregnancy (from 32 weeks) to protect the unborn child from infection.

The risk of infection from mother to child is highest during birth. If an elevated level of HBsAg is found during this testing, further tests are performed to assess the activity of the infection.