TBI testing is desirable whenever feasible to identify people at highest risk for developing TB disease.It is not required for people with HIV or in household contacts aged < 5 years. In HIV-negativehousehold contacts aged ≥ 5 years and in other risk groups TBI tests are recommended, but theirlack of availability should not be a barrier to providing TPT.The GDG noted that availability and affordability could determine which TBI test is used. Otherconsiderations include the structure of the health system, the feasibility of implementation andinfrastructure requirements.The incremental cost-effectiveness of IGRAs and TSTs appears to be influenced mainly by theiraccuracy. BCG vaccination decisively reduces the specificity of TST. The GDG noted, however, thatthe effect of BCG vaccination on the specificity of TST depends on the strain of vaccine used, the ageat which the vaccine is given and the number of doses administered. When BCG is given at birth, asrecommended by WHO and in practice in most parts of the world, it has a variable, limited impacton TST specificity (74). Therefore, the GDG agreed that a history of BCG vaccination has a limitedeffect on interpretation of TST results later in life. Hence, BCG vaccination should not be a determiningfactor in selecting a test.IGRA testing is more costly than TST and requires appropriate laboratory services. Operational difficultiesshould be considered in deciding which test to use. For example, IGRA requires a phlebotomy, whichcan be difficult, particularly in young children; it requires laboratory infrastructure, technical expertiseand expensive equipment; and its sensitivity is reduced in children aged < 2 years and those withHIV. Nevertheless, only a single visit is required to conduct an IGRA test (although patients may haveto make a second visit to receive the result). Skin testing with TST or TBST is less costly and can beperformed in the field, but it requires a cold chain, two health-care visits and training in intradermalinjection, reading and interpretation. One other practical advantage of IGRAs over TST is that theyare not susceptible to a “booster response”, which necessitates a two-step testing approach whenthe reactivity to TST has waned since infection.In 2011, WHO recommended use of three IGRA products for testing for TBI: QIAGEN QuantiFERON-Gold, QIAGEN QuantiFERON-TB Gold In-Tube and Oxford Immunotec T-SPOT.TB assays (75). In 2021,the list of WHO-recommended IGRAs was extended to include Beijing Wantai’s TB-IGRA and QIAGENQuantiFERON-TB Gold Plus (76).1. Recommendations 21The three specific TBST products available for review by the GDG that developed the 2022 WHOrecommendations were Cy-Tb (Serum Institute of India, India), Diaskintest® (Generium, RussianFederation) and C-TST (formerly known as ESAT6-CFP10 test, Anhui Zhifei Longcom, China). Usersof the tests might have to issue appropriate guidance and explain the difference between the TSTand TBSTs (64). It is also important to standardize measurement of the TBST reaction size and itsinterpretation. As for TSTs, use of TBSTs requires a cold chain, well-trained, skilled staff to administer andinterpret test results and multiuse vials for effective operational planning and batching. Procurementand stock management should be considered, including availability on the global market, as for anynew class of tests. TBSTs might require regulatory approval from national authorities or other relevantbodies, as they are a relatively new in-vivo tests.TST, TBST and IGRA are not validated for confirmation of TB disease and should therefore not be usedto diagnose TB nor for the diagnostic workup of adults being evaluated for TB disease.