Contact investigation in a primary school using a whole blood interferon-gamma assay

J Infect. 2009 May;58(5):352-7. doi: 10.1016/j.jinf.2009.02.019. Epub 2009 Apr 1.


Objectives: To evaluate the usefulness of QuantiFERON-TB Gold (QFT-G) for children.

Methods: Students in a primary school exposed to a tuberculosis patient were investigated using the tuberculin skin test (TST), chest X-ray examination and sequential QFT-G tests.

Results: The first QFT-G test was conducted one month after the end of exposure for 308 of the 313 children, with 6 (1.9%) positive. TST results were obtained from 306 of the students at 2 months after exposure, and 200 (65.4%) had induration > or =5mm. A second QFT-G test, a further month later, and a third QFT-G test, six months after exposure, found an additional 2 positive and one weakly positive, respectively. Overall, the rate of QFT-G positivity was 9.8% (4/41) for close contact children (> or =90h exposure), significantly higher than for casual contacts (< or =18h exposure; 1.8%, 5/272; p=0.020), whereas there was no significant difference in TST positive rates (p=0.078).

Conclusions: These data suggest that QFT-G has the same performance characteristics in BCG vaccinated children as it does in adults. The observation that none of the 297 students who were QFT-G negative had developed active TB after 3 years of follow-up suggests that QFT-G has a very high negative predictive value.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Biological Assay
  • Child
  • Female
  • Humans
  • Interferon-gamma / blood*
  • Male
  • Mass Screening / methods*
  • Middle Aged
  • Predictive Value of Tests
  • Reagent Kits, Diagnostic
  • Schools*
  • Tuberculin Test
  • Tuberculosis, Pulmonary / diagnosis*
  • Tuberculosis, Pulmonary / prevention & control


  • Reagent Kits, Diagnostic
  • Interferon-gamma