Serial testing of interferon-γ-release assays for the diagnosis of latent tuberculosis in hemodialysis patients

Abstract

The performance of serial interferon-gamma-release assays (IGRAs) for the diagnosis of latent tuberculosis has not been studied in hemodialysis patients. The QuantiFERON-TB-Gold In-Tube test (QFT) and T-SPOT-TB test (TSPOT) were performed 1 year after initial testing at a hemodialysis center. Ninety-eight patients were included in the final analysis. Positive rates for the initial tuberculin skin test (TST), QFT and TSPOT were 26.5%, 43.9% and 58.2%, respectively. The follow-up QFT and TSPOT showed positive responses in 52.0% and 53.1%. Conversion rates of the QFT and TSPOT were 20.0% and 26.8%. Reversion rates of the QFT and TSPOT were 16.3% and 29.8%; however, they decreased to 0.0% and 4.8% in patients with a concordantly positive response at the initial TST. A group at high risk for latent tuberculosis increased the risk for the TSPOT conversion [odds ratio (95% confidence interval), 7.76 (1.27-47.40)] and showed a trend of increasing the risk for the QFT conversion [1.97 (0.45-8.71)]. Reversion of both the QFT [18.92 (2.01-178.65)] and TSPOT [6.16 (1.57-24.19)] occurred more frequently in the group at low risk. Both conversion and reversion of the IGRAs were associated with the risk for latent tuberculosis in hemodialysis patients. However, serial IGRAs results should be interpreted cautiously due to their high variability.