Effect of prevention therapy for subclinical tuberculosis in child household contacts

<b>Background:</b> WHO guidelines emphasize child contact screening and TB preventive therapy (TPT) once TB disease is ruled out. However, in TB-exposed, TST-positive, asymptomatic children with radiological abnormalities compatible with TB, clinicians are often reluctant to initiate a curative treatment regimen due to concern for “overtreatment” or that preventive treatment in those with undetected TB disease may inadvertently lead to acquired drug resistance. <b>Methods:</b> We enrolled 793 TST-positive child household contacts (age≤15) who underwent both symptom and CXR screening in Lima, Peru. We followed them for the occurrence on TB disease over one year of follow-up. <b>Results:</b> Among the 793 contacts, 784 had a normal CXR and 451 received a 6-month isoniazid preventive therapy (IPT). In those with a normal CXR, the efficacy of IPT was 72% with incident TB occurring in 7 of 433 receiving IPT (1.6%) and 15 of 325 not receiving IPT (4.6%). In those with abnormal CXRs, IPT efficacy was 65% with TB occurring in 3/18 (17%) receiving IPT and 10/17 (59%) not receiving IPT (59%). <b>Conclusion:</b> We find that IPT reduces the occurrence of TB disease in TST- positive child contacts, even in those with radiographic lesions that may suggest subclinical TB.