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. At the GDG meeting, evidence was also presented on the individual- and community-level effects of screening of close contacts of TB patients. One trial of screening household contacts in Viet Nam showed a 2.5-fold increase in notification of contacts diagnosed with TB resulting from the intervention (relative risk [RR]: 2.5; 95% CI: 2.0–3.2), along with a 40% reduction in all-cause mortality among household contacts (RR: 0.6; 95% CI: 0.4–0.8) (22). Another trial of contact screening in South Africa and Zambia showed evidence that screening household contacts may reduce TB prevalence in the larger community after 4 years during which contact investigation is conducted, although this did not reach statistical significance (prevalence ratio: 0.82; 95% CI: 0.64–1.04); there was also a suggestion that the intervention reduced the transmission of TB, measured through the incidence of TB infection in schoolchildren (RR: 0.45; 95% CI: 0.20–1.05) (see Web Annex B, Table 3, and Web Annex C, Table 2) (15).
Eligibility for TPT should be assessed among all TB contacts who are screened and found not to have indications of TB disease (20). Children aged < 5 years who are household and close contacts of people with bacteriologically confirmed pulmonary TB and who are found not to have TB disease after appropriate clinical evaluation or according to national guidelines should be given TPT even if testing for TB infection is unavailable. Children aged ≥ 5 years, adolescents and adults who are household and close contacts of people with bacteriologically confirmed pulmonary TB who are found not to have TB disease after appropriate clinical evaluation or according to national guidelines may also be given TPT. Contacts of TB patients who are living with HIV, no matter what their age, in whom TB disease has been ruled out, should receive TPT as part of a comprehensive package of HIV care (20).