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

Abstract

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. 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. 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). 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.