The interferon gamma release assay (IGRA) test is a blood test used to see whether a person has been exposed to the tuberculosis (TB) bacteria.
The IGRA test is used to diagnose TB infection. This is when the TB bacteria is in the body but the person is not experiencing any symptoms suggestive of TB disease.
The Interferon Gamma Release Assay (IGRA) is a blood test used to see whether a
person has been infected with Mycobacterium tuberculosis ( the bacteria causing TB). The IGRA test works by measuring
the body’s immune response to the TB bacteria.
An IGRA test may be used to diagnose latent TB infection. It is not used to test
for active TB disease. A negative IGRA means that you probably don’t have the
TB bacteria in your body. A positive IGRA test means that at some point in time you
have probably been infected with the TB bacteria. This is called latent TB
Latent TB infection is when a person has the TB bacteria in their body but the immune
system is stopping the infection causing disease. Latent TB infection causes no
symptoms and cannot be passed on to other people.
There is a small risk that latent TB infection can progress to TB disease. The risk is increased in young children and old people, as well as people with weak immune systems. TB disease develops if the TB bacteria start to multiply and cause symptoms, such as a fever, unexpected weight loss, tiredness or a cough that won’t go away. Latent TB infection can be treated with special antibiotics to prevent it from progressing to TB disease in the future.
The Tuberculin Skin Test (TST), also known as a Mantoux test, is another test for
latent TB infection. It involves a small injection just under the skin, usually
on the forearm.
Your nurse or doctor will explain the advantages and disadvantages of the different tests and advise which test is most suitable for your situation. In some
situations both TST and IGRA may be required.
It is important to let the nurse or doctor know if you:
These conditions may affect the test result.
You will need to return to your doctor or chest clinic for the test result a few
days later. Your nurse or doctor will explain the result and whether any more tests or treatment is required.