Comparison of the sensitivity and specificity of two whole blood interferon-gamma assays for M. tuberculosis infection.
OBJECTIVE
To compare the sensitivity and the specificity of the QuantiFERON-TB Gold (QFT-G) and QuantiFERON-TB Gold In Tube (QFT-GIT) diagnostic tests for Mycobacterium tuberculosis infection.


METHODS
One-hundred patients with culture and/or PCR confirmed M. tuberculosis infection and 168 volunteers with no risk factors for M. tuberculosis infection were tested to estimate sensitivity and specificity, respectively.


RESULTS
Analysis of data from the tuberculosis (TB) patients with valid results found the sensitivity of QFT-GIT (92.6%, 87/94) to be significantly higher than that for the QFT-G test (81.4%, 79/97; p=0.023). The specificity of both QFT-GIT and QFT-G was 98.8% (CI: 95.1%-99.8%) with 2 of the 160 low risk subjects with valid results for both tests being positive. Data analysis confirmed the manufacturer's recommended test cut-off as being optimal, but identified higher sensitivity could be obtained by using a lower cut-off, with only a moderate decrease in specificity.


CONCLUSIONS
The QFT-GIT test had enhanced sensitivity for detection of M. tuberculosis infection over the QFT-G test, whilst maintaining equivalent high specificity. The logistic benefits of the QFT-GIT test format, as well as its higher sensitivity, should enable enhanced TB control.
Harada
Nobuyuki
N
The Research Institute of Tuberculosis, 3-1-24, Matsuyama, Kiyose City, Tokyo 204-8533, Japan. harada@jata.or.jp
Higuchi
Kazue
K
Yoshiyama
Takashi
T
Kawabe
Yoshiko
Y
Fujita
Akira
A
Sasaki
Yuka
Y
Horiba
Masahide
M
Mitarai
Satoshi
S
Yonemaru
Makoto
M
Ogata
Hideo
H
Ariga
Haruhiko
H
Kurashima
Atsuyuki
A
Wada
Akihiko
A
Takamori
Mikio
M
Yamagishi
Fumio
F
Suzuki
Kiminori
K
Mori
Toru
T
Ishikawa
Nobukatsu
N
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D007371:Interferon-gamma / Q000097:blood*; D008297:Male; D008875:Middle Aged; D009169:Mycobacterium tuberculosis; D011933:Reagent Kits, Diagnostic; D012680:Sensitivity and Specificity; D014376:Tuberculosis / Q000175:diagnosis* / Q000276:immunology / Q000382:microbiology; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis* / Q000276:immunology / Q000382:microbiology
D011933:Reagent Kits, Diagnostic; D007371:Interferon-gamma