Comparison of the QuantiFERON-TB Gold In-Tube test with the tuberculin skin test for detecting latent tuberculosis infection in hemodialysis patients

Abstract

Background and objectives: Hemodialysis (HD) patients are at increased risk of reactivation of latent tuberculosis (TB) infection (LTBI). LTBI screening of this population is recommended. The QuantiFERON-TB Gold assay (QFT-G) may be more accurate than the tuberculin skin test (TST) in the detection of LTBI. We prospectively compared the results of QFT-G to TST in HD patients.

Methods: We examined 100 patients and performed TST and QFT-G tests. Data obtained from patients and medical records included medical history (past history of TB, Bacillus Calmette-Guerin [BCG] vaccination, history of contact with previous TB cases), radiography reports (chest x-ray with changes consistent with old TB), and basic laboratory findings.

Results: Forty-three of 100 patients (43%) had a positive QFT-G test result and 34 (34%) had a positive TST test result. Overall agreement between the QFT-G and the TST was 65% (concordance [k]=0.26, P=0.01). Discordant test results were seen in 13 TST-positive/QFT-G-negative patients and in 22 TST-negative/QFT-G-positive patients. Before BCG vaccination and radiographic reports (of old TB changes) were associated with discordant test results. On multivariate analysis, a positive QFT-G test was associated with contact with previous TB cases (P=0.026) and radiographic report (P=0.034), whereas a positive TST test also was associated with a history of BCG vaccination (P=0.015).

Conclusions: QFT-G test results were more closely associated with TB risk factors than were positive TST results. Additionally, the QFT-G test was not affected by BCG vaccination. We concluded that QFT-G test is a more useful diagnostic method than TST for detecting LTBI in HD patients.