The evaluation of the Quantiferon-TB Gold test in pulmonary and extrapulmonary tuberculosis

In our study we evaluated the Quantiferon-TB Gold (QFT-G) test and compared it with tuberculin skin test (TST) positivity in 44 pulmonary and 21 extrapulmonary tuberculosis cases in whom active tuberculosis infection was suspected on clinical, microbiologic and radiologic grounds. QFT-G positivity was 75% in pulmonary tuberculosis and 76.2% in extrapulmonary tuberculosis. TST positivity was 68.2 and 62%, respectively. Although QFT-G positivity was higher than TST positivity, the difference was statistically insignificant (P=0.77). Similar to TST, QFT-G is one of the supplementary diagnostic tests for active tuberculosis disease and latent tuberculosis infection. Its advantage over TST is that it gives a result on the same day and it is unaffected by prior BCG and previous exposure to atypical mycobacteria. In conclusion, we think that, as with TST, a positive QFT-G result can be an adjunct to diagnosis in patients having clinical and radiological data compatible with tuberculosis.