TB

During the physical exam, your doctor will check your lymph nodes for swelling and use a stethoscope to listen to the sounds your lungs make when you breathe.

The most commonly used diagnostic tool for tuberculosis is a skin test, though blood tests are becoming more commonplace. A small amount of a substance called tuberculin is injected just below the skin on the inside of your forearm. You should feel only a slight needle prick.

Within 48 to 72 hours, a health care professional will check your arm for swelling at the injection site. A hard, raised red bump means you're likely to have TB infection. The size of the bump determines whether the test results are significant.

Results can be wrong

The TB skin test isn't perfect. Sometimes, it suggests that people have TB when they don't. It can also indicate that people don't have TB when they do.

You can have a false-positive result if you've been vaccinated recently with the bacille Calmette-Guerin (BCG) vaccine. This tuberculosis vaccine is seldom used in the United States but is widely used in countries with high TB infection rates.

False-negative results also can occur.

Blood tests

Blood tests can confirm or rule out latent or active tuberculosis. These tests measure your immune system's reaction to TB bacteria.

These tests require only one office visit. A blood test might be useful if you're at high risk of TB infection but have a negative response to the skin test, or if you've recently received the BCG vaccine.

Imaging tests

If you've had a positive skin test, your doctor is likely to order a chest X-ray or a CT scan. This might show white spots in your lungs where your immune system has walled off TB bacteria, or it might reveal changes in your lungs caused by active tuberculosis.

Sputum tests

If your chest X-ray shows signs of tuberculosis, your doctor might take samples of your sputum — the mucus that comes up when you cough. The samples are tested for TB bacteria.

Sputum samples can also be used to test for drug-resistant strains of TB. This helps your doctor choose the medications that are most likely to work. Getting results of these tests can take four to eight weeks.

With treatment, TB can almost always be cured. A course of antibiotics will usually need to be taken for 6 months.

Several different antibiotics are used because some forms of TB are resistant to certain antibiotics.

If you're infected with a drug-resistant form of TB, treatment with 6 or more different medications may be needed.

If you're diagnosed with pulmonary TB, you'll be contagious for about 2 to 3 weeks into your course of treatment.

You will not usually need to be isolated during this time, but it's important to take some basic precautions to stop the infection spreading to your family and friends.

You should:

stay away from work, school or college until your TB treatment team advises you it's safe to return

always cover your mouth when coughing, sneezing or laughing

carefully dispose of any used tissues in a sealed plastic bag

open windows when possible to ensure a good supply of fresh air in the areas where you spend time

avoid sleeping in the same room as other people 

If you're in close contact with someone who has TB, you may have tests to see whether you're also infected. These can include a chest X-ray, blood tests, and a skin test called the Mantoux test.

Read more about treating TB

Vaccination for TB

The BCG vaccine offers protection against TB, and is recommended on the NHS for babies, children and adults under the age of 35 who are considered to be at risk of catching TB.

The BCG vaccine is not routinely given to anyone over the age of 35 as there's no evidence that it works for people in this age group.

At-risk groups include:

children living in areas with high rates of TB

people with close family members from countries with high TB rates

people going to live and work with local people for more than 3 months in an area with high rates of TB

If you're a healthcare worker or NHS employee and you come into contact with patients or clinical specimens, you should also have a TB vaccination, irrespective of age, if:

you have not been previously vaccinated (you do not have a BCG scar or the relevant documentation), and

the results of a Mantoux skin test or a TB interferon gamma release assay (IGRA) blood test are negative