The definitions below apply to terms as used in these guidelines, and they may have different meanings elsewhere.
Active (tuberculosis) case-finding (ACF): Provider-initiated screening and testing in communities by mobile teams, often using mobile X-ray and rapid molecular tests. The term is sometimes used synonymously with “systematic screening”.
Computer-aided detection (CAD): The use of specialized software to interpret abnormalities on chest radiographs that are suggestive of TB. The results are expressed as abnormality scores. CAD may be used for screening or triage.
Enhanced (tuberculosis) case-finding: Health information or education, or awareness campaigns to provide information about what type of health-seeking behaviour is appropriate when people experience symptoms of TB; this type of case-finding may be combined with improving access to diagnostic services. Enhanced case-finding may or may not be combined with screening.
Initial screening: The first screening test, examination or other procedure applied in the population eligible for screening.
Number needed to screen (NNS): The number of persons that need to undergo screening in order to diagnose one person with TB disease.
Passive case-finding: A patient-initiated pathway to TB diagnosis involving: (1) a person with TB disease who experiences symptoms that he or she recognizes as serious; (2) the person having access to and seeking care, and presenting spontaneously at an appropriate health facility; (3) a health worker correctly assessing that the person fulfils the criteria for presumptive TB; and (4) successful use of a diagnostic algorithm with sufficient sensitivity and specificity to diagnose TB.
Repeat screening: This refers to rescreening the same population at a given interval.
Risk groups: Any group of people in which the prevalence or incidence of TB is significantly higher than in the general population.
Screening test, examination or procedure for tuberculosis disease: A test, examination, or other procedure used to distinguish people with a high likelihood of having TB disease from people who are highly unlikely to have TB. A screening test is not intended to be diagnostic. People with positive results on a screening test should undergo further evaluation, depending on the screening algorithm used.
Second screening: A second screening test, examination or other procedure undergone by persons whose results were positive during the initial screen.
Systematic screening for TB disease: The systematic identification of people at risk for TB disease, in a predetermined target group, by assessing symptoms and using tests, examinations or other procedures that can be applied rapidly. For those who screen positive, the diagnosis needs to be established by one or several diagnostic tests and additional clinical assessments. This term is sometimes used interchangeably with “active tuberculosis case-finding”. It should be distinguished from testing for TB infection (with a TB skin test or interferon-g release assay).
Triage: The process of deciding the diagnostic and care pathways for people based on their symptoms, signs, risk markers and test results. Triaging involves assessing the likelihood of various differential diagnoses as a basis for making clinical decisions. It can follow more- or less-standardized protocols and algorithms, and it may be done in multiple steps.
Triage test for TB: A test that can be rapidly conducted among people presenting to a health facility to differentiate those who should have further diagnostic evaluation for TB from those who should undergo further investigation for non-TB diagnoses.
Tuberculosis disease: The disease state caused by Mycobacterium tuberculosis. It is usually characterized by clinical manifestations, which distinguish it from TB infection without signs or symptoms (previously referred to as latent TB infection). Also referred to as active tuberculosis.