Screening

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”.

People in prisons and other penitentiary institutions are at an increased risk for TB compared with the general population, and they often have limited access to health care services. The estimated incidence of TB among people residing in prisons is 23 times higher than that among the general population (24). Data reviewed for the GDG meeting suggest that screening in prisons may improve early case detection, increase overall case detection and reduce TB prevalence.

Children and adolescents are of particular importance in contact screening, given the high prevalence found in the youngest age groups and the importance of rapid diagnosis and treatment owing to the risk of rapid disease progression in children younger than 5 years(23), as well as the importance of initiating preventive treatment if TB disease has been ruled out (see Section 2.4.2).

Household and close contacts of individuals with TB disease are at high risk of TB infection and developing TB disease. A systematic review conducted for the guideline update found the weighted pooled prevalence of TB disease among all close contacts of TB patients was 3.6% (95% confidence interval [CI]: 3.3–4.0), with a median NNS of 35 (95% CI: 17–65). Systematic screening has been strongly recommended since 2012 for contacts of individuals with TB disease {21}, given the high prevalence of disease in this population.

The evidence reviewed about the performance of symptom screening among children and adolescents younger than 15 years who are close contacts of someone with TB included 4 studies with a total of 2 695 participants (see Web Annex B, Table 17, and Web Annex C, Table 10).

None of the screens investigated reached the target product profile of 90% minimum sensitivity in these high-risk subpopulations of children, although CXRs came the closest. Concerns were noted about the risk of incorporation bias when using a composite reference standard in this group, thus potentially inflating the estimates of accuracy observed.

The evidence reviewed about the performance of symptom screening (any one of current cough, fever, poor weight gain or close contact with someone with TB) included 2 studies conducted in the outpatient setting with a total of 20 926 participants and including 20 3135 screens (see Web Annex B, Table 19, and Web Annex C, Table 10).

For the purpose of this guideline, systematic screening for TB disease is defined as the systematic identification of people at risk for TB disease, in a predetermined target group, by assessing using tests, examinations or other procedures that can be applied rapidly. The screening tests, examinations and other procedures should efficiently distinguish people with a high probability of having TB disease from those who are unlikely to have TB disease.