[Utility of QuantiFERON TB-2G for tuberculosis contact investigations in public health services].

ABSTRACT

OBJECTIVE: The objective of the present study was to examine the utility of QuantiFERON TB-2G (QFT) in tuberculosis contact investigations performed by a public health center. METHODS: Adachi City Public Health Center, Tokyo, started using QFT in its laboratory service in June, 2005. The results of QFT, as well as tuberculin skin tests (TSTs) performed in tuberculosis contact investigations in the 10 month period since then were here analyzed. QFT was carried out for 67 contacts two months after their last contact with the index case. TST was given simultaneously. RESULTS: Of the total of 67 contacts investigated during the period, 9 were positive for QFT, 5 were doubtful positive, and the remaining 53 were negative. Among 48 subjects tested with TST, 22 had strong reactions with erythema > or = 30 mm, out of which 4 were positive for QFT. In addition, there were 5 QFT-positives among the remaining 26 with weak tuberculin reactions. These 9 subjects with positive QFT were indicated for chemoprophylaxis. CONCLUSIONS: Adachi City Public Health Center is pioneering the application of new technology for detection of latent tuberculosis infection in contact investigations of the inhabitants. As expected from trial findings, QFT was shown to be a useful tool in a practical setting for the purpose of detecting TB infection, with greater accuracy than with TST, independent of the history of BCG vaccination. This approach can help avoid both over-diagnosis and under-diagnosis.