Background: Interferon-gamma release assays are increasingly being used in low-incidence settings, but there is little information on whether test results influence clinical decisions in children.
Methods: In June 2009, the Montreal Children's Hospital began implementing the QuantiFERON-TB Gold In-Tube (QFT) as a follow-up test to the tuberculin skin test (TST). Pediatric respirologists were asked to document how the QFT result changed their initial clinical management based on the TST.
Results: During a 2-year period, 399 children with TST and QFT results were recruited prospectively. The median age was 13 years. In the cohort, 83% were foreign-born and 82% were Bacille Calmette-Guérin vaccinated. The QFT was negative in 5 of 11 (45.5%) children diagnosed with active tuberculosis (TB). Among 55 TST+/QFT- children evaluated as TB contacts, the negative QFT changed the treatment decision in only 3 (5.5%), and isoniazid was prescribed to the remainder. In 201 TST+/QFT- children from targeted school and immigrant screening programs, a negative QFT result was used to withhold isoniazid in 145 (72.1%) children. These children were followed for 1 year, during which no TB cases occurred. In a multivariable analysis, history of TB contact and TST induration ≥20 mm were associated with fewer changes in clinical decisions.
Conclusions: Our cohort study showed that pediatric respirologists used negative QFT results to withhold isoniazid in most low-risk children who were referred for a positive TST found through targeted screening programs. In contrast, in almost all TST-positive children who were evaluated as TB contacts, negative QFT results did not change clinical management.