High prevalence of latent tuberculosis infection in dialysis patients using the interferon-gamma release assay and tuberculin skin test

Abstract

Background and objectives: Patients in ESRD on hemodialysis with latent tuberculosis (TB) infection have 10 to 25 times the risk of reactivation into active disease compared with healthy adults. This study investigates the prevalence of latent TB infection in dialysis patients from a country with an intermediate burden of TB and its associated risk factors using the QuantiFERON-TB Gold in-tube test (QGIT) and the tuberculin skin test (TST).

Design, setting, participants, & measurements: This was a prospective, cross-sectional study performed at a medical center in Taiwan on dialysis patients. Each patient underwent QGIT, two-step TST using 2 tuberculin units (TU) of PPD RT-23, a chest x-ray to exclude active TB, and an interview to determine TB risk factors.

Results: Ninety-three of 190 eligible patients were enrolled: 35 men and 58 women. 64.8% were vaccinated with the Bacille-Calmette-Guérin (BCG) vaccination. Overall, 34.4% were positive by QGIT and 10.8% were indeterminate. Using a 10-mm TST cutoff, 53.9% were positive. There was poor correlation between TST and QGIT at any TST cutoff criteria. There was a significant increasing trend of QGIT positivity with age in those younger than 70 years, and, conversely, a decreasing trend of TST reactivity with age. Significant risk factors for QGIT positivity included age and past TB disease.

Conclusions: This study shows a high prevalence of latent TB infection in dialysis patients in a country with an intermediate burden of TB. QGIT in dialysis patients correlated better than TST with the risk of TB infection and past TB disease.

Figure 1.

Distribution of TST induration and the booster effect of a two-step TST in dialysis patients.

Figure 2.

Association of age with the prevalence of latent TB infection in dialysis patients using the QGIT and the TST and association of age with indeterminate responses of QGIT. *Test for trend: OR 0.65, 95% CI 0.43 to 0.99, P = 0.05. **Test for trend excluding age ≥70 years: OR 1.93, 95% CI 1.04 to 3.58, P = 0.04. Overall agreement between QGIT and TST excluding indeterminate results: 57.8%, κ = 0.16.