Tuberculin skin test for the diagnosis of latent tuberculosis during renal replacement therapy in an endemic area: A single center study

Patients on renal replacement therapy (RRT) are at-risk for developing tuberculosis (TB). There is limited information on tuberculin skin test (TST) and its predictability for development of TB. In this prospective cohort study, patients taken for RRT were included. Patients with active TB were excluded. TST was done with 5-tuberculin unit. In addition to TST, age, sex, diabetes as basic disease, number of dialysis and blood transfusion (BT), pre-transplant TB, hepatitis B and C infections and type of immunosuppression were correlated with the development of TB. Of the 200 patients included, TST was positive in 21 and negative in 179. In TST negative group, 20 (11.1%) and in TST positive group 5 (23.8%) patients developed TB. TB free survival in two groups was similar (P = 0.08). On multivariate Cox regression analysis, hazard of development of TB by TST was 2.7 [P = 0.11, confidence interval (CI) 0.78-9.7]. There was no difference between TST non-responsive and TST negative patients (P = 0.18). Sensitivity and specificity of TST for predicting TB was only 20 and 9%, respectively. Our study shows that TST in patients on dialysis is an insensitive and nonspecific test to predict development of active TB.