Concordance of the Tuberculin skin test and T-SPOT®.TB test results in kidney transplant candidates

Detection of latent tuberculosis infection (LTBI) in transplant candidates is very important. Th e tuberculin skin test (TST) and interferon-gamma release assays (IGRAs) are standard immunologic tools for LTBI detection. Th e aim of this study was to compare the TST results and T-SPOT® .TB test (a type of IGRAs) in kidney transplant candidates for the screening of LTBI and follow the patients with positive test for an activation of tuberculosis (TB) after transplantation and using anti-TB prophylaxis.

Th is study was a prospective study and carried out in 44 renal transplant candidates from March 2010 to February 2011 in the teaching hospitals of Isfahan University of Medical Sciences, Iran. TST and T-SPOT® .TB test were performed and their results evaluated. Patients with a positive skin test and/or T-SPOT® .TB test were started on anti-TB prophylaxis and followed after transplantation for an activation of their LTBI for 1 year.

Overall, 8 (18.2%) patients were positive for TST and 6 (13.6%) patients for T-SPOT® .TB test. Th e agreement between TST and T-SPOT® .TB test was moderate (κ = 0.49, 95% confi dence interval 0.145-0.839). Th e overall agreement between TST and T-SPOT® .TB test was 86%. No relation was found between the underlying diseases and TST or T-SPOT® .TB test positivity. Although isoniazid prophylaxis was used for patients with positive TST and/or T-SPOT® .TB test, one patient had reactivation of TB.

In kidney transplant candidates both TST and T-SPOT® .TB test were comparable for the diagnosis of LTBI with reasonable agreement between the tests. However, further studies are needed to determine the ability of T-SPOT® .TB test to detect LTBI and to evaluate the need for prophylaxis in these patients.