Missed opportunities for prevention of tuberculosis in children

All children with tuberculosis (TB) represent a missed opportunity for preventive therapy — theoretically. Of course, not all children with TB will have an identifiable source case because, in TB-endemic settings, exposure and infection do occur to varying degrees beyond the known, inner circle of the ‘household’. Nonetheless, risk factors for TB infection are well known and include clinical characteristics of the source case such as degree of sputum smear-positivity along with closeness and duration of contact. Risk factors for developing disease following infection are also recognised and the risk to children is greatest in the youngest and the immunosuppressed. These risk factors provide the logic for the importance given to a contact history in the clinical approach to diagnosis of TB in young children and for the universally recommended contact-screening. Contact screening has two main aims: (1) to identify contacts of any age who are symptomatic and so need further investigation and management for possible TB disease, and (2) contacts who do not have active TB disease but require preventive therapy (or chemoprophylaxis) because they are at high risk of disease following infection. Preventive therapy has proven efficacy in significantly reducing the risk of disease in high-risk groups and is widely recommended for child contacts who are young (0–4 years) or HIVinfected irrespective of age. However, proven effectiveness of preventive therapy in child contacts in the high-burden setting is not established because contact-screening and management are rarely implemented. A study by Du Preez et al. in this issue of Annals of Tropical Paediatrics highlights again the lack of routine implementation of chemoprophylaxis while providing original and important data on its potential effectiveness. The data are considerably strengthened by microbiological confirmation of TB diagnosis in all children included in the study. Of those eligible for preventive therapy, the majority (71%) represented a missed, recorded opportunity with the source case commonly being a parent. The study emphasises the importance of young age as an opportunity and as a consequence of missed opportunity. Most identifiable, missed opportunities were in children aged ,3 years. This is expected, given the increased likelihood of the contact being known to the young child compared with older, more socially mobile children. Further, disseminated disease and death were common in this same group of infants and young children. Timely provision of preventive therapy would have prevented up to 200 of the reported TB cases and a number of TB-related deaths. As acknowledged by the authors, a limitation of the study is the uncertain accuracy of the contact history data collected retrospectively from medical records. However, this might have resulted in under-reporting, thereby providing an underestimate of missed opportunities rather than over-reporting because recording was not prospective or standardised when the contact history data were collected. Careful documentation of contact history is always important and likely to improve identification of TB exposure in children. Screening consistently finds a high prevalence of TB infection among child contacts, and preventive therapy significantly reduces the risk of disease. Why do opportunities to prevent disease among this vulnerable group continue to be Annals of Tropical Paediatrics (2011) 31, 297–299