Clinical utility of the QuantiFERON TB-2G test for elderly patients with active tuberculosis.
OBJECTIVE
To evaluate the response to the QuantiFERON-TB-2 Gold (QFT-2G) test (Cellestis Ltd; Carnegie, VIC, Australia) in elderly patients with active tuberculosis (TB) to determine whether the QFT-2G test might be a feasible method for diagnosing TB infection in this group of patients.


METHODS
The subjects were 30 elderly patients with active TB and 100 younger patients with active TB. The QFT-2G test results were analyzed in relation to combined and separate responses to early secretory antigenic target 6-kD (ESAT-6) protein and culture filtrate protein 10 (CFP-10) antigens.


RESULTS
Of the 30 elderly patients with active TB, 27% had a positive tuberculin skin test (TST) result and 77% had a positive QFT-2G test result. Of the 100 younger patients with active TB, 70% had a positive TST result and 87% had a positive QFT-2G test result. Although there was no significant difference between the two patient groups in the positive rate for the QFT-2G test results (p = 0.185), there was a significant difference in the rates of positive TST results between the elderly and younger patients (p = 0.012). The positive test result rate for both ESAT-6 and CFP-10 antigens in the elderly patients (17%) was significantly lower than that in younger patients (37%; p = 0.038). There was an indeterminate result for the QFT-2G test in five elderly patients, and this might have been related to the presence of lymphocytopenia due to underlying disease. A negative result on the QFT-2G test was detected in two elderly patients, and this might have been related to the severity of the active TB.


CONCLUSIONS
We confirmed that the QFT-2G test might be a more useful method of diagnosing TB infection than the TST for elderly patients if peripheral lymphocyte counts have been preserved.
Kobashi
Yoshihiro
Y
Division of Respiratory Diseases, Department of Medicine, Kawasaki Medical School, 577 Matsushima, Kurashiki, 701-0192, Japan. yoshihiro@med.kawasaki-m.ac.jp
Mouri
Keiji
K
Yagi
Shinich
S
Obase
Yasushi
Y
Miyashita
Naoyuki
N
Okimoto
Niro
N
Matsushima
Toshiharu
T
Kageoka
Takeshi
T
Oka
Mikio
M
D000368:Aged; D000369:Aged, 80 and over; D000942:Antigens, Bacterial / Q000097:blood* / Q000276:immunology; D001202:Ascitic Fluid / Q000382:microbiology; D001426:Bacterial Proteins / Q000097:blood* / Q000276:immunology; D015415:Biomarkers / Q000097:blood; D001992:Bronchoalveolar Lavage Fluid / Q000382:microbiology; D003937:Diagnosis, Differential; D005240:Feasibility Studies; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007159:Immunologic Tests / Q000706:statistics & numerical data*; D008297:Male; D008875:Middle Aged; D009169:Mycobacterium tuberculosis / Q000276:immunology / Q000302:isolation & purification; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013183:Sputum / Q000382:microbiology; D014374:Tuberculin Test; D014376:Tuberculosis / Q000097:blood / Q000175:diagnosis* / Q000382:microbiology
D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D015415:Biomarkers; C117940:CFP-10 protein, Mycobacterium tuberculosis; C093276:ESAT-6 protein, Mycobacterium tuberculosis