Screening

Contact screening can be difficult. Once the contacts of a TB patient have been identified, they should be screened for TB symptoms and/or undergo CXR, followed by appropriate diagnostic evaluation (4, 5). Tracing of household contacts usually identifies many close contacts who are eligible for screening and TPT; however, it is expensive and time-consuming for health-care workers to identify the contacts of all known TB patients.

As for adults, tuberculin skin tests and interferon-g release assays should not be used to screen for TB disease in children (12, 34), as these tests cannot distinguish TB infection from TB disease and cannot predict who will progress to TB disease. Both tests may be influenced by mechanisms unrelated to TB infection and give false-negative or false-positive results. The role of these tests in decision-making for TPT is discussed elsewhere (4, 5).

mWRDs are not currently recommended for screening for TB disease in children < 15 years.

The sensitivity for TB of “any abnormality” as reported on CXR in children is 84%, and the specificity is 91%. It is thus more specific than symptom screening alone.

Child contacts are at high risk of TB disease, and the risk varies substantially by age. Newborn infants are at particularly high risk of infection with TB if the mother had untreated TB disease when they were born. Apart from the risk of exposure because of close proximity to adults in a household with TB, children < 5 years who are infected with TB have a 19% chance of progression to TB disease within 2 years (39). Most paediatric mortality occurs in this age group, with 80% of paediatric deaths from TB occurring in children < 5 years (40).

It is estimated that, in 2019, approximately 1.2 million children under 15 years of age fell ill with TB, and 230 000 died of TB (2). In about 56% of the 1.2 million patients, TB was not diagnosed or reported, the proportion being highest in children < 5 years of age (65%). The symptoms of TB are underrecognized in children because they are less specific and overlap with those of common childhood diseases, often leading to delayed diagnosis. Children are more prone to extrapulmonary forms of TB, which may challenge timely detection.

The algorithms for screening children are listed in Fig. A.5.1-A.5.6 in Annex 5.

Eleven algorithm options are proposed for screening of people living with HIV for TB that include the new and existing screening tools presented in this section (see Annex 3). (See 3.3 for an introduction and discussion of screening algorithms in general, including the definitions and implications of single, parallel, sequential positive and sequential negative screening algorithms.)

All the screening tests described above, when positive or abnormal, identify adults and adolescents living with HIV who have a higher probability of TB disease and who are then to be referred for diagnostic evaluation. TB diagnosis among people living with HIV should include use of an mWRD as a diagnostic test (12), LF-LAM where indicated (12), and other clinical, radiological or laboratory procedures as necessary.