Tb test when is it read

In general, there is no risk associated with repeated tuberculin skin test placements. If a person does not return within hours for a tuberculin skin test reading, a second test can be placed as soon as possible. A boosted reaction occurs mainly in previously infected, older adults whose ability to react to tuberculin has decreased over time. When given a TST years after infection, these persons may have an initial negative reaction.

However, the TST may stimulate the immune system, causing a positive or boosted reaction to subsequent tests. Vaccination with live viruses, including measles, mumps, rubella, oral polio, varicella, yellow fever, BCG, and oral typhoid, may interfere with TST reactions. For persons scheduled to receive a TST, testing should be done as follows:. There are two kinds of tests that are used to determine if a person has been infected with TB bacteria: the TB blood test and the TB skin test.

The tests measure the response of TB proteins when they are mixed with a small amount of blood. Only one visit is required to draw blood for this test. Health care providers are encouraged to use newer TB blood tests to screen for TB infection. In order to prevent false-positive reactions, TB blood tests are also the preferred method of TB testing for people 5 years of age and older who have received the BCG TB vaccine.

A diagnosis of latent TB infection is made if a person has a positive TB test result and a medical evaluation does not indicate TB disease.

TB disease is diagnosed by medical history, physical examination, chest x-ray, and other laboratory tests. TB disease is treated by taking several drugs as recommended by a health care provider. There are several treatment regimens for the treatment of latent TB infection. These regimens use the drugs isoniazid, rifapentine, or rifampin.

Short-course regimens include: Three months of once-weekly isoniazid plus rifapentine 3HP , four months of daily rifampin 4R , or three months of daily isoniazid plus rifampin 3HR. Short-course latent TB infection treatments are effective, are safe, and have higher completion rates than longer treatments. If a short-course treatment regimen is not an option, 6H or 9H is an effective alternative latent TB infection treatment regimen. Skip directly to site content Skip directly to page options Skip directly to A-Z link.

Tuberculosis TB. Section Navigation. Facebook Twitter LinkedIn Syndicate. Fact Sheets. Additional tests are needed to determine if the person has latent TB infection or TB disease. There is no problem in repeating a TB skin test. If repeated, the additional test should be placed in a different location on the body e.

Two TB blood tests are approved by the U. TB test T-Spot. Skip directly to site content Skip directly to page options Skip directly to A-Z link. Tuberculosis TB. The indurated area should be measured across the forearm perpendicular to the long axis. People who have been vaccinated with BCG should not be exempted from TB skin testing unless they have a documented positive result from a prior test.

Two-step TSTs are not recommended for patients in other settings. The first "step" may stimulate or boost the immune system's ability to react to the test. If the second "step" is not performed as part of baseline screening, a subsequent positive TST reaction could be misinterpreted as a new infection. BCG is used in many countries with a high prevalence of TB to prevent childhood tuberculous meningitis and miliary disease. However, BCG is not generally recommended for use in the United States because of the low risk of infection with Mycobacterium tuberculosis , the variable effectiveness of the vaccine against adult pulmonary TB, and the vaccine's potential interference with tuberculin skin test reactivity.