Tuberculosis FACT SHEETS

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Diagnosing active TB disease

There are three steps in diagnosing active tuberculosis (TB) disease:

1. a complete medical history and medical examination
2. a chest x-ray
3. laboratory tests

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1 During the medical history, your doctor will want to know if you have any symptoms of TB disease. The doctor will also want to know if you have been exposed to a person with active, infectious TB, if you have had a previous diagnosis of latent TB infection or active TB disease, or if you have any other risk factors for developing active TB disease.

2 A chest x-ray is used to look for evidence of active TB disease in your lungs.

3 The third step is a series of laboratory tests. If your doctor thinks you have active TB disease in your lungs, you will be asked to give a sputum (phlegm) sample. If your doctor thinks you have active TB disease outside of your lungs, you may have to give other types of samples.

Your sputum sample (or smear) is examined under a microscope. It is cultured (or grown) to find out if it contains the TB germ (bacteria). A positive culture confirms that you have active TB disease.

After your sample has been cultured, it is tested to find out if the type of TB you have is resistant to any TB drugs. The results of these tests can help your doctor choose the right drugs to treat you.

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