641—155.37 (125,135) Definitions. For the purpose of these rules, the following definitions shall apply:
“Bacille Calmette-Guerin (BCG) vaccination” means a vaccine for TB. BCG is used in many countries with a high prevalence of TB to prevent childhood tuberculosis meningitis and military disease. 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.
“Baseline TB screening” means the screening of staff and residents for latent tuberculosis infection (LTBI) and TB disease at the beginning of employment or upon admission to a facility. Baseline TB screening includes a symptom screen for all staff and residents and tuberculin skin tests (TSTs) or interferon-gamma release assay (IGRA) for Mycobacterium tuberculosis for those staff and residents with previous negative test results for M. tuberculosis infection.
“Baseline TST”  or “baseline IGRA”  means the TST or IGRA, respectively, that is administered at the beginning of employment to newly hired staff or upon admission to residents of facilities.
“Boosting” means a phenomenon in which a person has a negative TST (i.e., false-negative) result years after infection with M. tuberculosis and then a positive subsequent TST result. The positive TST result is caused by a boosted immune response of previous sensitivity rather than by a new infection (false-positive TST conversion). Two-step testing reduces the likelihood of mistaking a boosted reaction for a new infection.
“Extrapulmonary TB” means TB disease in any part of the body other than the lungs (e.g., kidney, spine, or lymph nodes).
“Interferon-gamma release assay”  or “IGRA”  means a whole-blood test that can aid in diagnosing Mycobacterium tuberculosis infection.
“Laryngeal TB” means a form of TB disease that involves the larynx and may be highly infectious.
“Latent TB infection”  or “LTBI”  means infection with M. tuberculosis without symptoms or signs of disease having manifested.
“Mantoux method” means a skin test performed by intradermally injecting 0.1 mL of purified protein derivative (PPD) tuberculin solution into the volar or dorsal surface of the forearm.
“Pulmonary TB” means TB disease that occurs in the lung parenchyma, usually producing a cough that lasts three weeks or longer. Pulmonary TB is usually infectious.
“Purified protein derivative (PPD) tuberculin” means a material used in diagnostic tests for detecting infection with M. tuberculosis.
“Risk classification” means the category on which the infection control team, or designated other, determines the setting’s TB risk classification is based, as a result of the TB risk assessment.
“Serial screening” refers to TB screening performed at regular intervals following baseline TB screening. Serial TB screening, also called annual or ongoing TB testing, consists of two components: (1) assessing for current symptoms of active TB disease, and (2) testing for the presence of infection with M. tuberculosis by administering either a TST or single IGRA.
“Symptom screen” means a procedure used during a clinical evaluation in which patients are asked if they have experienced any departure from normal in function, appearance, or sensation related to TB disease (e.g., cough).
“TB patient” means a person who had undiagnosed infectious pulmonary or laryngeal TB while in the facility during the preceding year. “TB patient” does not include persons with LTBI (treated or untreated), extrapulmonary TB disease, pulmonary, or laryngeal TB who have met criteria for noninfectiousness.
“TB risk assessment” means an initial and ongoing evaluation of the risk for transmission of M. tuberculosis in a particular health care setting.
“TB screening” means an administrative control measure in which evaluation for LTBI and TB disease is performed through baseline and serial screening of staff and residents of facilities.
“TB screening plan” means a plan that facilities develop and implement that comprises four major components: (1) baseline testing for M. tuberculosis infection, (2) serial testing for M. tuberculosis infection, (3) serial screening for signs or symptoms of TB disease, and (4) TB training and education.
“Treatment for LTBI” means treatment that prevents the progression of M. tuberculosis infection into TB disease.
“Tuberculin skin test”  or “TST”  means a diagnostic aid for finding M. tuberculosis infection. The Mantoux method is the recommended method to be used for the TST.
“Tuberculosis”  or “TB”  means the namesake member organism of M. tuberculosis complex and the most common causative infectious agent of TB disease in humans. In certain instances, the species name refers to the entire M. tuberculosis complex, which includes M. bovis and M. african, M. microti, M. canetti, M. caprae, and M. pinnipedii.
“Tuberculosis disease”  or “TB disease”  means a condition caused by infection with a member of the M. tuberculosis complex that has progressed to causing clinical (manifesting symptoms or signs) or subclinical (early stage of disease in which signs or symptoms are not present, but other indications of disease activity are present) illness.
“Two-step tuberculin skin test”  or “two-step TST”  means the procedure used for the baseline skin testing of persons who will receive serial TSTs to reduce the likelihood of mistaking a boosted reaction for a new infection.
[ARC 1926C, IAB 4/1/15, effective 5/6/15]