Boosted tuberculin skin testing in hemodialysis patients

Abstract

Tuberculosis remains a significant health problem for patients receiving long-term hemodialysis (HD). The tuberculin skin test (TST) is an important method of detecting Mycobacterium tuberculosis infection. Cutaneous anergy decreases the accuracy of the test in these patients. Higher and repeating doses have been mentioned in the immunosuppressed patients. This study examined the significance and frequency of the booster phenomenon in 2-step tuberculin testing of these patients. A total of 106 outpatients in a hospital-based HD center in Turkey were screened with 5 and 10 tuberculin units (TU) and Candida antigen. To determine the frequency of booster phenomenon, patients with <10 mm indurations to the initial TST with 5 TU were given a second test with 10 TU, 7 days later. Forty (37.7%) of 106 patients had a significant tuberculin reaction (>or=10 mm) on the initial TST with 5 TU. The booster effect was detected in 16 (24.3%) of 66 patients who had a negative reaction (<or=10 mm) to the initial test. Overall, 56 (52.8%) patients showed a significant reaction on both tests. Anergy was found in 39 (36.8%) of 106 patients. Even with the high rate of anergy, TST seems to be useful for these patients; also, it is inexpensive and easy to perform. We suggest repeating the test with higher doses in patients with a high risk for tuberculosis. Anergy testing with Candida antigen may be helpful in determining the value of TST.