[Usefulness of QuantiFERON TB-2G in contact investigation of a tuberculosis outbreak in a university].
OBJECTIVE
This study examined the usefulness of QuantiFERON TB-2G (QFT) i.e., a novel technique for detecting tuberculosis infection based on the whole blood interferon-gamma response to specific antigens, in the investigation of a tuberculosis outbreak among university students.


METHODS
One university student was diagnosed as smear-positive pulmonary tuberculosis. In order to determine the extent of tuberculosis infection among contact students, tuberculin skin tests and QFT were performed on the close-contact group (220 people), as well as on the non-close-contact group (242 people).


RESULTS
Nine students were found to be TB either clinically or on the X-ray screening in the contact investigation. In the close-contact group, the QFT-positive rate was 32.7%. The proportion of those exhibiting tuberculin reactions with erythema diameters of 30 mm or larger was 57.7%. In the non-close-contact group, the QFT-positive rate was only 0.8 %, as expected from the current healthy Japanese youths of this age. In contrast, strong tuberculin reactions with erythema of 30 mm or larger were seen in 18.2% in the latter group, most likely due to the previous history of BCG vaccination.


CONCLUSIONS
QFT was clearly demonstrated to be a useful method for diagnosing tuberculosis infection, especially among subjects who show tuberculin reactivity due to past BCG vaccination. At the same time, the current criteria for the indication of chemoprophylaxis based on the strong tuberculin reaction were considered to be unreliable, causing many subjects with strong reactions to be given unnecessary preventive medications.
Funayama
Kazushi
K
Yokohama City Kohoku Public Health and Welfare Center, 26-1, Daizutocho, Kohoku-ku, Yokohama-shi, Kanagawa 222-0032 Japan. ka00-funayama@city.yokohama.jp
Tsujimoto
Aiko
A
Mori
Masaaki
M
Yamamoto
Hiromi
H
Fujiwara
Keiko
K
Nishimura
Tomoyasu
T
Hasegawa
Naoki
N
Horiguchi
Itsuko
I
Mori
Toru
T
Marui
Eiji
E
D000328:Adult; D000942:Antigens, Bacterial / Q000276:immunology*; D016358:Contact Tracing / Q000379:methods; D004196:Disease Outbreaks / Q000706:statistics & numerical data; D006801:Humans; D007371:Interferon-gamma / Q000097:blood*; D009169:Mycobacterium tuberculosis / Q000276:immunology*; D014374:Tuberculin Test; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis*; D014495:Universities
D000942:Antigens, Bacterial; D007371:Interferon-gamma