Preventive TB treatment refers to decreasing the risk of a first or recurrent episode of TB. A first episode of TB may occur in someone exposed to infection or with latent infection.A recurrent episode of TB occurs in someone who has previously had TB.
a) Aimed at decreasing the risk of a first episode of TB
People at high risk of developing TB may benefit from preventive treatment, as an intervention currently for individual benefit rather than as a public health measure to control TB. For example, WHO has for many years recommended isoniazid preventive treatment (IPT) for children who are household contacts of infectious index cases of TB, and who, after screening, are found not to have TB.
WHO and UNAIDS recommend IPT for 6 months for tuberculin-positive HIV-infected individuals who do not have TB. However, even where tuberculin testing is not feasible, IPT may still be valuable in HIV-infected individuals at high risk of TB. Among PLWH, IPT is likely to provide protection against the risk of developing TB through two mechanisms. Firstly, by decreasing the risk of progression of recent infection, and secondly, by decreasing the risk of reactivation of latent M. tuberculosis infection. In populations with high TB prevalence, the duration of benefit following completion of a 6-month course of IPT is limited (up to 2.5 years).This is probably due to continued exposure to M. tuberculosis infection. The duration of protection depends on the duration of preventive treatment.
b) Aimed at decreasing risk of a recurrent episode of TB
Among TB patients who complete SCC,the recurrence rate is higher in HIV-positive than in HIV-negative TB patients. Post-treatment prophylaxis (for example with isoniazid) can decrease the risk of TB recurrence in HIV-infected individuals, although it does not prolong survival. Further studies are needed to confirm the benefit, establish the optimum regimen (drugs and duration), and assess operational feasibility, before treatment aimed at decreasing risk of TB recurrence can be recommended.
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