title: Contact investigation in a primary school using a whole blood interferon-gamma assay.
abstract: OBJECTIVE
  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.
authors.affiliation: The Research Institute of Tuberculosis, Japan Anti-Tuberculosis Association, Kiyose City, Tokyo, Japan. higuchi@jata.or.jp
authors.forename: Kazue
authors.initials: K
authors.lastname: Higuchi
authors.forename: Shuji
authors.initials: S
authors.lastname: Kondo
authors.forename: Masako
authors.initials: M
authors.lastname: Wada
authors.forename: Sawako
authors.initials: S
authors.lastname: Hayashi
authors.forename: Gorou
authors.initials: G
authors.lastname: Ootsuka
authors.forename: Noboru
authors.initials: N
authors.lastname: Sakamoto
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Harada