Positive TB Skin-Test Results

Tuberculosis (TB) is is a bacterial infection. It usually attacks the lungs, but it can spread and attack other areas of the body. There are two types of TB: active TB disease and latent TB infection. The purpose of the TB skin test is to determine whether your immune system responds to an injection of the TB bacterium.

Statistics

• According to the Centers for Disease Control and Prevention, one third of the world's population is infected with TB. Each year, there are two million TB-related deaths worldwide and nine million people become sick with TB.

Testing

• There are two kinds of tests to detect TB infection: the TB skin test (TST) and a TB blood test. You should be tested if you have been in contact with a person known to have active TB, if you have symptoms, if you inject illegal drugs or if you work in a health-care or housekeeping position. A skin test will require a needle injection of tuberculin into the skin on the forearm. The skin in the test area is usually checked for any abnormalities before administering the injection. There will be a pale skin elevation that means the test was administered properly.

Identification

• A nurse or a doctor will read the skin test within 48 to 72 hours after the injection in order to look for a reaction on the skin. The person who performs the examination will look for localized swelling and see if it is hard or raised. Redness is not a part of the measuring of a TB skin test, as it can often be a natural reaction. However, if someone has blisters, the test will also be considered positive.

False Positives

• The TB skin test does not provide 100 percent accuracy and can be misconstrued due to an underlying health condition, such as kidney disease or diabetes. There are those with TB who can have a negative test result and vice versa. False positives in testing can occur if you were recently exposed to TB, if you have a weakened immune system or if you have had a recent live-virus vaccination such as smallpox or measles.

Symptoms

• Some who have TB may not present with symptoms and may not be able to spread the disease. Common symptoms include chest pain or excessive coughing, coughing up blood or mucus, sudden weight loss, fever, fatigue, sweating, chills and changes in appetite. Although TB normally attacks the respiratory system, it is possible to have pain in the back, blood in the urine or other problems depending on the location of the infection. People with latent TB can develop the disease in the future.

Diagnostic Tests

• If someone has a positive TB skin test, a doctor will probably require that you have further testing, such as a chest X-ray to determine whether the bacteria is in the lungs or culture tests to determine whether bacteria is present in bodily secretions such as mucus. These additional tests will help determine whether the TB skin test was accurate and the best method of treatment.

Treatment

• Most people who have a positive TB skin test will require some form of treatment because they are considered a carrier of the infectious disease. Treatment for latent TB infection, which can cause a positive TB skin test, is isoniazid and may need to be taken for up to a year. The medication will destroy bacteria and reduce the chance that it will become active.