Old standard treatment (initial phase ISHT or SHE; continuation phase IIHT or HE)
The recurrence rate is higher in HIV-positive than in HIV-negative TB patients. In one study of TB/HIV patients, there was an association between recurrence and cutaneous reaction to thioacetazone.A severe thioacetazone reaction necessitated interruption of treatment and a change to ethambutol. There are several possible explanations for the link between increased risk of recurrence and thioacetazone reaction. These include treatment interruption, subsequent poor compliance, more advanced immunocompromise, and change to the combination of isoniazid and ethambutol in the II-month continuation phase.
Among TB patients who complete SCC, the recurrence rate may be higher in HIV-positive than in HIV-negative patients. Studies suggest two ways of reducing this higher recurrence rate, although they do not prolong survival. One way is to extend the duration of the treatment regimen from 6 to I2 months. Another way is to give post-treatment prophylaxis (for example with isoniazid). Further studies are needed before these treatments can be widely recommended. Studies are still needed to confirm the benefit, establish the optimum regimen (drugs and duration) and assess operational feasibility.
Recurrence: relapse or reinfection?
When TB recurs after previous cure, there are 2 possibilities:
a) true relapse (reactivation of persisters not killed by anti-TB drugs);
b) reinfection (due to re-exposure to another source of infection). The risk of re-infection depends on the intensity of exposure to TB transmission.
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