Contribution of Xpert® MTB/RIF to the diagnosis of pulmonary tuberculosis among TB-exposed children in The Gambia

SETTING: Greater Banjul Area, The Gambia.
OBJECTIVE : To conduct a pragmatic evaluation of the Xpert® MTB/RIF assay in the diagnosis of tuberculosis (TB) among child contacts.
DESIGN: In this prospective study, one induced sputum sample was obtained from TB contacts aged ,15 years and tested using fluorescent microscopy, culture and Xpert. The diagnostic accuracy of the microbiological tests was evaluated against culture and 'all TB diagnosis and treatment' as separate reference standards.
RESULT S : Using culture as a reference standard, Xpert was positive for Mycobacterium tuberculosis in 6/14 culture-positive and 6/473 culture-negative children, giving a sensitivity and specificity of respectively 42.9% (95%CI 17.7-71.1) and 98.7% (95%CI 97.2-99.5). With 'all TB diagnosis and treatment' as a composite reference standard, combined Xpert and culture tests were positive for M. tuberculosis in 20/62 children with TB disease (32.3%, 95%CI 20.9-45.3), which was comparable to the yield from microscopy, culture and Xpert combined (33.9%, 95%CI 22.3-47.0), but significantly higher than individual yields from each test.
CONCLUSION: The sensitivity of Xpert is low in actively traced child contacts, but a combination of Xpert and mycobacterial culture has incremental benefits for the bacteriological confirmation of TB disease.