Tuberculin Skin Test Results and the Booster Phenomenon in Two-Step Tuberculin Skin Testing in Hemodialysis Patients

Abstract

Patients with chronic renal failure are at increased risk for tuberculosis (TB). Centers for Disease Control and Prevention (CDC) have recommended annual skin testing for TB, with tuberculin-purified protein derivative (PPD), in patients with chronic renal failure. Uremia alters the macrophage function, which can lead to anergy for skin tests. The aim of this prospective study was to determine the prevalence of positive tuberculin skin test (TST) and the booster effect of TST in hemodialysis patients living in a relatively underdeveloped portion of the country. Material and Methods. Patients were recruited from Van (Yuzuncu Yil University Hospital, Yuksek Ihtisas Hospital) and the Mus State Hospital). At the time of this study, a total of 143 patients were under hemodialysis treatment in these hemodialysis centers, and among them, 124 were included in the study. Informed consent was obtained before inclusion in the study. A positive PPD was an induration of >10 mm in response to five tuberculin units of PPD (RT23-Tween 80), at 72 h. TST-negative patients received a booster TST 10 days later, similar to 10 cm away from the previous intracutaneous injection. The test dose could not be increased due to unavailability of this kind of preparation. The test was performed and interpreted in the same way. Skin testing was performed in June and December 2003. Patients with known active TB are not included in the study. Testing was not done in hospitalized patients to rule out effects of other disease states. Results. Mean age of the patients was 45.3 +/- 16 (range 13-82) years. All patients were on HD treatment twice (n: 14) or three times (n: 110) weekly. Duration of dialysis before TST was 30 +/- 17 (12-84) months. With the first test (n: 14), 11.3% of the patients showed a positive reaction; the second test added (n: 15) 12.1% more TST-positive patients, reaching a total of (n: 29) 23.4% of the patients with a positive TST. The mean induration of the positive TST was 16 +/- 4 mm in the first test and 15 +/- 3 mm in the second. Five (17.2%) of the patients with positive PPD and two of the patients (2.1%) with negative PPD results subsequently developed active TB within 12 months. Conclusion. We found a significant booster effect in our hemodialysis patients using TST-2. Repeat PPD test with the same dosage could detect positive patients more than twofold higher. Among positive PPD patients, TB incidence is considerably high.