Clinical evaluation of the T-SPOT.TB test for patients with indeterminate results on the QuantiFERON TB-2G test.
OBJECTIVE
To evaluate the clinical utility of the T-SPOT.TB test for patients with indeterminate results on the QFT-2G test.


METHODS
Forty patients (10.6%) showed indeterminate results among 378 patients who underwent QFT-2G test because active TB disease was clinically suspected. T-SPOT.TB test was performed for these 40 patients before the initiation of antituberculous treatment.


RESULTS
Forty patients (10.6%) were judged as showing indeterminate results on QFT-2G test because the positive control presented a lower IFN-gamma level. Elderly patients (68.2 versus 57.7) or immunocompromised patients receiving immunosuppressive treatments and patients with a decrease in lymphocyte count, serum protein and albumin were more frequently recognized in the patients with indeterminate results compared to those with determinate results on QFT-2G test. T-SPOT.TB test could clearly demonstrate the results in 26 of the 40 patients (65.0%) with indeterminate results of QFT-2G test; these were divided into six patients with positive results and 20 with negative results of T-SPOT.TB test. Elderly patients (73.5 versus 64.3) or patients with underlying diseases such as malignant disease and those receiving immunosuppressive treatment and patients with hyponutritional conditions were more frequently recognized in the patients with indeterminate results compared to patients with determinate results on both tests.


CONCLUSIONS
We think it may be necessary to introduce T-SPOT.TB test to increase the diagnostic rate of TB disease including latent tuberculosis infection because indeterminate results of QFT-2G test might be further decreased using T-SPOT.TB test. Although 14 patients showed indeterminate results on both tests, the lymphocytes of these patients may not possess functional cytokine production activity.
Kobashi
Yoshihiro
Y
Division of Respiratory Diseases, Department of Medicine, Kawasaki Medical School, Kurashiki, Japan. yoshihiro@med.kawasaki-m.ac.jp
Sugiu
Tadaaki
T
Shimizu
Hiroki
H
Ohue
Yoshihiro
Y
Mouri
Keiji
K
Obase
Yasushi
Y
Miyashita
Naoyuki
N
Oka
Mikio
M
D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007371:Interferon-gamma / Q000032:analysis*; D008297:Male; D008875:Middle Aged; D011933:Reagent Kits, Diagnostic; D012680:Sensitivity and Specificity; D014374:Tuberculin Test; D014376:Tuberculosis / Q000175:diagnosis* / Q000276:immunology
D011933:Reagent Kits, Diagnostic; D007371:Interferon-gamma