Agreement between the results of tuberculin skin test and Interferon-Gamma Release Assays in renal transplant candidates.

Introduction: Identification of latent tuberculosis (TB) infection is important in kidney transplant candidates. Due to the absence of a gold standard, both tuberculin skin test (TST) and interferon-gamma release assays (IGRA) are used to screen patients. The aim of this study was to evaluate the agreement of these two tests in patients undergoing renal transplantation.

Materials and Methods: Two hundred kidney transplant candidates at a referral center in 2014-2017 were included in this study. TST and Quantiferon-Gold (QFT-G) tests were performed for all patients before transplantation. In case of a positive result in any of the tests, patients were administered a 9-month prophylaxis treatment using isoniazid. Cohen's kappa coefficient (k) test was used to determine the agreement between the two tests.

Results: The mean age of patients was 40.72 ± 18.33. Nine (4.5%) patients had positive TST and 16 (8%) had positive IGRA. Concordance of the two tests was evaluated as medium (κ = 0.44 and P < 0.001). No association was found between the underlying causes of renal failure and skin test positive or IGRA. The tests showed a poor agreement among diabetics, candidates of re-transplantation, and those who were on dialysis for longer than a year (κ < 0.20).

Conclusion: TST or IGRA can be used to screen TB in kidney transplant candidates with a moderate agreement. However, we suggest using both TST and QFT-G in diabetics, re-transplant candidates, and those on dialysis for >1 year.