Operational Handbooks

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.

The algorithms for screening adults and adolescents ≥ 10 years of age living with HIV are presented in Fig. A.3.1-A.3.11 in Annex 3.

The CAD for TB detection calibration tool has been developed for analysis of the data collected in the CAD calibration protocol described above. The tool estimates the primary outcomes of yield and cost at every possible CAD threshold, including yields of true-positive, true-negative, false-positive and false-negative results; sensitivity and specificity; negative and positive predictive values; proportions of prevalent TB cases diagnosed and missed; and cost implications, including total costs for diagnostic evaluation and cost per true case detected.

A toolkit has been developed jointly by the WHO Global Tuberculosis Programme and the Special Programme for Research and Training in Tropical Diseases for conducting a CAD calibration study in a new setting. The toolkit consists of three parts.

The choice of screening and diagnostic algorithms should be based on:

This operational handbook includes 10 screening algorithm options for screening the general population and groups at higher risk (not including people living with HIV or children), consisting of a combination of one or two screening tests and a diagnostic evaluation (Annex 1). Algorithms for screening people living with HIV are discussed in Chapter 5 and algorithms for screening children in Chapter 6.