[Difficulties of TB diagnosis in children: QuantiFERON TB Gold In-Tube as useful tool]

Diagnosis of childhood tuberculosis (TB), active TB or latent tuberculosis infection (LTBI), is complicated by uncommon clinical, radiological and bacteriological features. The tuberculin skin test (TST) is imperfect: difficulty of the intradermal injection for the child, lack of sensibility and specificity. The stop of the systematic inoculation by the BCG since July 2007, in France, could lead to an increase of the incidence of the childhood TB. It is urgent to find new diagnostic tools: sensitive, specific, fast, of objective reading and little expensive. Interferon-gamma assays could be useful but the data are still insufficient in paediatrics and sometimes contradictory. A prospective study which compared the usefulness of QuantiFERON TB Gold In-Tube (QFT-IT) assay with TST to detect LTBI or active disease in 51 children was realised in University Hospital of Nancy. This allowed us to confirm interest of QFT-IT; however, surprisingly, very discordant QFT-IT and TST results were obtained (only five children were QFT-IT+/TST+). A high number (14%) of indeterminate QFT-IT occurred, without explanation by pre-analytical or clinical parameters. Further studies are needed to demonstrate the usefulness of this assay in diagnosing LTBI and particularly active TB in children.