Use in routine clinical practice of two commercial blood tests for diagnosis of infection with Mycobacterium tuberculosis: a prospective study.
BACKGROUND
Two commercial blood assays for the diagnosis of latent tuberculosis infection--T-SPOT.TB and QuantiFERON-TB Gold--have been separately compared with the tuberculin skin test. Our aim was to compare the efficacy of all three tests in the same population sample.


METHODS
We did a prospective study in 393 consecutively enrolled patients who were tested simultaneously with T-SPOT.TB and QuantiFERON-TB Gold because of suspected latent or active tuberculosis. 318 patients also had results available for a tuberculin skin test.


RESULTS
Overall agreement with the skin test was similar (T-SPOT.TB kappa=0.508, QuantiFERON-TB Gold kappa=0.460), but fewer BCG-vaccinated individuals were identified as positive by the two blood assays than by the tuberculin skin test (p=0.003 for T-SPOT.TB and p<0.0001 for QuantiFERON-TB Gold). Indeterminate results were significantly more frequent with QuantiFERON-TB Gold (11%, 43 of 383) than with T-SPOT.TB (3%, 12 of 383; p<0.0001) and were associated with immunosuppressive treatments for both tests. Age younger than 5 years was significantly associated with indeterminate results with QuantiFERON-TB Gold (p=0.003), but not with T-SPOT.TB. Overall, T-SPOT.TB produced significantly more positive results (38%, n=144, vs 26%, n=100, with QuantiFERON-TB Gold; p<0.0001), and close contacts of patients with active tuberculosis were more likely to be positive with T-SPOT.TB than with QuantiFERON-TB Gold (p=0.0010).


CONCLUSIONS
T-SPOT.TB and QuantiFERON-TB Gold have higher specificity than the tuberculin skin test. Rates of indeterminate and positive results, however, differ between the blood tests, suggesting that they might provide different results in routine clinical practice.
Ferrara
Giovanni
G
Section of Respiratory Disease, Department of Oncology, Haematology, and Respiratory Disease, University of Modena and Reggio Emilia, Via del Pozzo, 71-41100 Modena, Italy.
Losi
Monica
M
D'Amico
Roberto
R
Roversi
Pietro
P
Piro
Roberto
R
Meacci
Marisa
M
Meccugni
Barbara
B
Dori
Ilaria Marchetti
IM
Andreani
Alessandro
A
Bergamini
Barbara Maria
BM
Mussini
Cristina
C
Rumpianesi
Fabio
F
Fabbri
Leonardo M
LM
Richeldi
Luca
L
D000369:Aged, 80 and over; D002675:Child, Preschool; D004641:Emigration and Immigration; D005260:Female; D006403:Hematologic Tests / Q000379:methods*; D006801:Humans; D007223:Infant; D008297:Male; D015203:Reproducibility of Results; D012882:Skin Tests / Q000379:methods*; D014376:Tuberculosis / Q000175:diagnosis*