|
|
      |
|
 |
Tuberculin skin test (TST)Tuberculin skin tests (TST) are administered to detect the presence of Mycobacterium tuberculosis, the bacterium that causes tuberculosis (TB). The terms Mantoux, TB skin test, tuberculin skin test, and PPDs are often used interchangeably. Mantoux refers to the technique for administering the test. Tuberculin (also called purified protein derivative or PPD) is the solution used to administer the test. The preferred term for the test is tuberculin skin test, or TST. On this page: TST BasicsThe TST is an intradermal injection of 0.1 ml of tuberculin (PPD) on the inner surface of the forearm. The skin test reaction should be read between 48 and 72 hours after administration. If the test is not read within 72 hours, another TST should be placed unless the amount of induration is ≥ 10 mm within 7 days after placement.
The reaction should be measured in millimeters of induration (palpable, raised, hardened area or swelling). Do not measure erythema (redness). The indurated area should be measured across the forearm (perpendicular to the long axis). Healthcare workers (HCWs), patients, or their family members should not be allowed to record their own TST results.
The cut-off points (PDF: 65KB/1 page) for a positive TST result depend on the individual’s risk factors for TB exposure or for developing active TB disease if infected. 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. Disregard BCG history when interpreting TST results. HCWs and patients with positive TST results must receive appropriate medical follow up. Two-Step TSTsA two-step TST is required for baseline TB screening of HCWs and patients in boarding care facilities, correctional facilities, and nursing homes who have not had a TST within the previous 12 months. Two-step TSTs are not recommended for patients in other settings. A two-step TST is performed at baseline because people who were infected with TB many years ago may have a negative reaction to an initial TST. 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. Follow the directions in the chart provided by the Centers for Disease Control and Prevention (CDC) to perform two-step TSTs. BCGBCG, or bacille Calmette-Guérin, is a vaccine for TB. 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. TSTs and TB blood tests to detect TB infection are not contraindicated for persons who have been vaccinated with BCG. Evaluation of TST reactions in persons vaccinated with BCG should be interpreted using the same criteria for those not BCG-vaccinated. Unlike the TST, blood tests for TB infection do not detect the presence of BCG and are less likely to give a false-positive result. Training ResourcesBCG Vaccine Mantoux Tuberculin Skin Test Models Kits (PDF: 95KB/1 page) Mantoux Tuberculin Skin Test Training Materials Kit Mantoux Tuberculin Skin Testing Wall Chart Tuberculin Skin Testing Fact Sheet If you have questions or comments about this page, use our IDEPC Comment Form or call 651-201-5414 (TTY: 651-201-5797) for the MDH Infectious Disease Epidemiology, Prevention and Control Division. |
|
Updated Friday, 12-Jun-2009 15:53:37 CDT
