Value of the tuberculin skin test in screening for tuberculosis in dialysis patients

Background. Hemodialysis patients are at high risk for tuberculosis, and a tuberculin skin test (TST) is not usually helpful in detecting tuberculosis infection because of anergic reactions. Prophylactic therapy against tuberculosis in dialysis patients is important to enhance transplantation success. Herein we evaluated the value of TST in screening for tuberculosis and analyzed any compounding factors that might affect the results of the test in hemodialysis patients in an endemic area of Turkey. Methods. A total of 187 (96 female, 91 male) patients were screened using a 2-step TST. Test results were compared with clinical, radiologic, and laboratory data. Results. None of the patients had active tuberculosis during the study and 55% had been vaccinated against tuberculosis. After the first purified protein derivative (PPD) test, 55.1% of the patients showed a positive reaction, ultimately reaching a total of 68.4% following the second test. Cumulative positive TST results were significantly correlated with male gender (P =.001, r =.352), previous tuberculosis history (P =.013, r =.183) p ositively, whereas with the ferritin level (P =.001, r = -.233) negatively; but there were no significant relationships between TST results and other data. Conclusions. Impairment of delayed-type hypersensitivity reaction is frequent in dialysis patients, but we observed high rates of positivity with the two-step TST which could be attributed to tuberculosis being endemic in Turkey. Further comparative studies with more specific diagnostic methods will be helpful to evalute the importance of TST positivity in identifying tuberculosis-infected HD patients.