Immunodiagnosis of tuberculosis infection in children under the age of five - Which testing is feasible?

Abstract

Immunodiagnosis of tuberculosis infection (TB) in children under the age of five is challenging. Current German guidelines recommend tuberculin skin testing (TST), but not interferon gamma release assays (IGRAs) as first line diagnosis. In 71 TB exposed, non BCG vaccinated and asymptomatic children under the age of five TST (cut off < 5mm) and IGRA (QuantiFERON TB Gold in tube) were performed simultanously. In four children (6%) the IGRA was inconclusive. In seven (10%) of the remaining 67 children both TST and IGRA were positive. One of those children had pulmonary TB. In one child only the TST and in five children (7%) only the IGRA was positive. One of these children developed active TB during the follow up. Conflicting results were detected in six children (9%) in total. All children with negative tests were treated with isoniazide (INH) for three months, all children with at least one positive test result were treated with INH/rifampicine for three months. This study shows that there is a number of inconclusive IGRAs in children under the age of five. Therefore, IGRAs should not replace the TST in TB diagnosis in this age group. Nevertheless, they could add sensitivity to the results of the TST testing.