Detecting Latent Tuberculosis Infection Prior to Kidney Transplantation in a Tertiary Hospital in Saudi Arabia: Comparison of the T-SPOT.TB Test and Tuberculin Test

Background: Tuberculosis (TB) remains a major worldwide public health problem with over 8.8 million newly diagnosed cases in 2010. Patients with end-stage renal disease (ESRD) who are on hemodialysis (HD) have a significantly higher incidence of Mycobacterium tuberculosis infection or disease than healthy individuals. Most cases of active tuberculosis (TB) in patients with ESRD are due to the reactivation of a latent infection, and this patient group is at roughly 10- to 25-fold higher risk for reactivating TB infection than the general population. Candidates for solid organ transplantation are routinely screened for latent tuberculosis infection (LTBI). In this study we aimed to compare Tuberculin Skin Test (TST) with T-SPOT.TB, for the detection of LTBI in candidates for kidney transplantation.
Methods: Prospective study of 133 HD Patients who did not have a diagnosis of active TB diseases or LTBI previously referred, through a 5-month period, to our institutions. Forty four kidney donors without evidence of renal insufficiency or immunocompromising conditions by medical history served as control group. All patients were tested with tuberculin (TST), and T-Spot.TB and the results were compared.
Results: In donors, the concordance between the T-SPOT and the TST was moderate (90.9 %, к=0.46). Forty of 44 donors (90.9%) had concordance results between the T-Spot TB and TST.In hemodialysis patients, the concordance between the T-SPOT.TB and the TST was poor (60.15 %, к=0.07). Fifty three of 133 patients (40%) had discordant results between the T-SPOT.TB and TST. Of these, 13 patients had a positive TST but negative T-SPOT.TB and 40 had a positive T-SPOT.TB but a negative TST.
Conclusion: Our data strongly argue against the use of TST in screening of LTBI in HD patients. T-SPOT.TB test in dialysis patients correlated better than TST with the risk of TB infection (e.g. increased age and low body mass index). It is a more reliable and powerful diagnostic tool than TST. However, further studies should be carried out to determine the tests with higher sensitivity and most permitted specificity.