Prognostic Value of a T-Cell–Based, Interferon-γ Biomarker in Children with Tuberculosis Contact

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   Figure. Study flow diagram.

   Study flow diagram detailing the follow-up of 908 children with complete baseline results for enzyme-linked immunospot (ELISpot) and tuberculin skin test (TST). IPT = isoniazid preventive therapy; IR = incidence rate.

   * Index patients and child contacts were recruited at the 7 government-run tuberculosis clinics in the Anatolian side of Istanbul.

   † Pediatric Infectious Disease Clinic at Marmara University Hospital, Istanbul.

   ‡ When sputum microscopy and culture reports for all 443 index cases were obtained and checked, 4 contacts had index cases who did not have sputum smear–positive results and 2 contacts had index cases whose sputum grew nontuberculosis atypical mycobacteria.

   § Two contacts were removed because of loss of ELISpot plates, and 33 contacts were removed because of an episode of bacterial contamination of peptide pool reagents.

   ∥ Twenty (5%) contacts had positive ELISpot results and 37 (7%) contacts had negative ELISpot results at recruitment.

   ¶ Isoniazid preventive therapy was administered on the basis of age and TST result and was interpreted in accordance with Turkish Ministry of Health guidelines. Eighteen contacts who had positive ELISpot and negative TST results at recruitment and 49 contacts who had negative ELISpot and TST results at recruitment were given IPT because their TST converted. In total, 688 contacts received IPT, of whom 41 were exposed to index cases with multidrug-resistant tuberculosis. Thirteen incident cases received IPT: 6 had positive ELISpot and TST results, 4 had positive ELISpot and negative TST results (2 of whom had converted TST results), and 3 had negative ELISpot and negative TST results (2 of whom had converted TST results). None of the incident cases had negative ELISpot and positive TST results.

   ** Per 1000 person-years of follow-up.