Screening

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.

The provider-initiated screening pathway to TB diagnosis entails systematic identification of people with possible TB disease in a predetermined target group with tests, examinations or other procedures that can be applied rapidly. In those with a positive screening test result, the diagnosis must be established by one or several diagnostic tests and additional clinical assessments, which together are highly accurate.