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.