Testing for TB

Testing for TB

If you are at high risk of TB, you should be given advice and information about the need for testing.

Everyone who has been in close contact (for example, sharing a bedroom, kitchen, bathroom or living room) with someone diagnosed with active TB may need testing to check whether they are infected. This is called 'contact tracing'.

Your local TB team should offer you testing if you are in close contact with someone you know who has TB in their lungs or larynx (part of the throat that contains their vocal cords). Other factors that will affect whether you are offered testing for TB include:

  • how much contact you had with the person with TB (for example, if you are a partner, parent, a hospital patient, or a student or work colleague of a person with TB)

  • where you work (for example, if you work in the NHS and have contact with patients or clinical samples or if you work in a prison)

  • where you live, or where you have lived (for example, people arriving in the UK from a country where TB is widespread, people who are homeless or in hostels, and people in prisons)

  • whether you have a weakened immune system

  • whether you have been in contact with a particularly infectious person.

Tests for TB

There are a range of tests for TB that you may be offered, depending on your circumstances. These include:

Mantoux test: a small amount of harmless TB protein is injected under the skin (you can't catch the disease from this test). The area is checked to see if your body has reacted to the TB protein 48–72 hours later.

Interferon‑gamma release assay: a blood test that is sometimes done after, at the same time as, or instead of, the Mantoux test. If the result is positive, you should have more tests to see whether you have TB.

Sputum smear: you may be asked to cough up a sputum specimen so that it can be examined for TB in the laboratory.

Chest X‑ray: you may be given a chest X‑ray to see whether you have TB in your lungs.

Depending on your risk and test results, you may be offered further tests or be referred to a TB specialist (see diagnosing active TB).

If your TB team thinks you are still at risk and you haven't already been vaccinated, you may be offered a vaccination called BCG (see BCG vaccination).

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