Usefulness of QuantiFERON TB-2G, a diagnostic method for latent tuberculosis infection, in a contact investigation of health care workers.
OBJECTIVE
To evaluate the usefulness of QuantiFERON TB-2G (QFT-2G) for detecting latent tuberculosis infection (LTBI) in a contact investigation of health care workers.


METHODS
The investigated subjects were 190 subjects among the health care workers who were examined between January 2005 and June 2006. Background information, including a past history of tuberculosis (TB) or tuberculin skin test (TST) or BCG vaccination, and contact score (infectivity x contact duration) were investigated. The TST and QFT-2G test were performed on all subjects.


RESULTS
In 109 subjects with a negative TST history, the TST results were converted to positive in 38 subjects. While the TST was positive in 48 subjects (25%), the QFT-2G test was positive in only five subjects (3%). The correlation of the QFT-2G with TST results was not significant. There was no relationship between contact score and the TST result. Twenty-nine subjects had TST positive responses (22%), but there were no QFT-2G positive responses in subjects with a mild contact score. Sixteen subjects had TST positive responses (31%), but two subjects showed positive QFT-2G results (4%) in the moderate contact score group. However, the positive response rate of the TST and QFT-2G test was the same percentage in the severe contact score group (33%).


CONCLUSIONS
The QFT-2G test showed a significant relationship with the contact score when compared with the TST. If the subjects with LTBI in the moderate contact score group were selectively excluded, the contact investigation in the mild contact score group may not be necessary. If there would have been many subjects with the QFT-2G positive responses in the moderate contact score group, we think that the QFT-2G test must be performed even in the mild contact score group.
Kobashi
Yoshihiro
Y
Division of Respiratory Diseases, Department of Medicine, Kawasaki Medical School, Kurashiki. yoshihiro@med.kawasaki-m.ac.jp
Obase
Yasushi
Y
Fukuda
Minoru
M
Yoshida
Kouichiro
K
Miyashita
Naoyuki
N
Fujii
Masashi
M
Oka
Mikio
M
D000328:Adult; D003141:Communicable Diseases / Q000175:diagnosis* / Q000382:microbiology; D005260:Female; D006282:Health Personnel; D006801:Humans; D008297:Male; D011933:Reagent Kits, Diagnostic / Q000592:standards; D014374:Tuberculin Test / Q000379:methods* / Q000592:standards*; D014376:Tuberculosis / Q000175:diagnosis* / Q000382:microbiology
D011933:Reagent Kits, Diagnostic