Comparison of the tuberculin skin test and Quanti-FERON-TB Gold In-Tube [QFT-G] test for the diagnosis of latent tuberculosis infection in dialysis patients

ABSTRACT

Dialysis patients are more likely than the general population to develop active tuberculosis [TB]. In these patients, the availability of a highly sensitive and specific test to diagnose latent TB will ensure earlier treatment and decreased progression to active disease. In the current study, the Quanti-FERON-TB Gold In-Tube [QFT-G] test was compared with the tuberculin skin test [TST] for the diagnosis of latent tuberculosis infection [LTBI] among 200 hemodialysis patients and 15 confirmed TB disease cases in a tertiary care center in Saudi Arabia. Among the LTBI cases, 26 [13%] were TST positive, and 65 [32.5%] were positive by the QTF-G test, with an overall agreement between the 2 tests of 75.5% [k = 0.34] being observed. Among the confirmed tuberculosis disease cases, none were positive by TST, and 10 [66.7%] were positive by the QTF-G test, resulting in an overall agreement of 33.3% [k = 0]. A comparison between the TST and the QTF-G test was performed based on the sensitivity, specificity, and area under the curve [AUC] obtained for the tests. The QTF-G test was more sensitive and less specific than the TST in predicting the confirmed TB disease cases. When we tested the correspondence of the AUC values between the 2 diagnostic modalities, the obtained p-value was 0.0003. In conclusion, the AUCs of the examined diagnostic modalities are significantly different in predicting LTBI and tuberculosis