[Cost-effectiveness analysis of QuantiFERON-TB 2nd generation used for detection of tuberculosis infection in contact investigations].
OBJECTIVE
QuantiFERON-TB-2nd Generation (QFT) has recently been developed as an accurate tool for detecting tuberculosis infection regardless of past history of BCG vaccination. A cost-effectiveness analysis was made on the usefulness of QFT that was used in the contacts investigation of a group of subject exposed to tuberculosis infection.


METHODS
A model was built assuming that a group of youngsters was exposed to an infection source with different degrees of intensity. The distribution of the tuberculin reaction of this group was assumed to be variable according to the history of BCG vaccination and tuberculin testing. Also, the distribution of tuberculin reaction size after the recent exposure is assumed to be different, as has been observed previously. The strategies for investigating this group included giving QFT to subjects having erythema size exceeding 30 mm, 20 mm, and 10 mm as compared with the strategy with the tuberculin test only, or the QFT only. The outcome variables calculated for each strategy were sensitivity and specificity, and predictive values in detecting tuberculosis infection; the number of indications for chemoprophylaxis, the number of tuberculosis patients averted, and the costs incurred in treating tuberculosis patients and chemoprophylaxis cases and testing with tuberculin and QFT were also considered. The sensitivity (specificity) of the QFT employed in the analysis was 89% (98%) based on our observations.


CONCLUSIONS
It was confirmed that the additional use of QFT would greatly reduce the number of indications for chemoprophylaxis cases that have never been infected and that the use of QFT is cost effective in spite of its relatively high unit cost. It will be useful to decide on the eligibility of QFT testing, i.e., the minimal tuberculin reaction size of subjects to whom QFT is given, based on the assumption of pre-exposure distribution of tuberculin reaction size of the group.
Mori
Toru
T
Research Institute of Tuberculosis, JATA, 3-1-24, Matsuyama, Kiyose-shi, Tokyo 204-8533 Japan. tmori@jata.or.jp
Harada
Nobuyuki
N
D016358:Contact Tracing / Q000191:economics* / Q000295:instrumentation*; D003362:Cost-Benefit Analysis; D006801:Humans; D007371:Interferon-gamma / Q000097:blood; D007564:Japan; D008403:Mass Screening / Q000191:economics / Q000379:methods; D012680:Sensitivity and Specificity; D014374:Tuberculin Test; D014376:Tuberculosis / Q000175:diagnosis*
D007371:Interferon-gamma