Two-step tuberculin skin testing in our hospital employees

To evaluate the baseline values of tuberculin reaction, two-step tuberculin skin testing was carried out in 365 employees of our hospital. We defined strongly response group when the size of erythema showed more than 30 mm or who showed strongly positive reaction. Two-step tuberculin skin testing was carried out in 165 hospital employees excluding those who were defined as the strongly response group in the first testing. 80 hospital employees (48.5%) became strongly response group by the second tuberculin skin testing. Altogether, 76.7% of all employees were strongly response group either by the first time or the second tuberculin skin testing. The size of erythema and that of induration showed 13.2 +/- 12.6 mm (mean +/- SD), 6.9 +/- 9.2 mm increase, respectively, in the two-step tuberculin skin testing, so-called Booster phenomenon. We could not know the true tuberculin reaction status by the single tuberculin skin testing. Therefore, two-step tuberculin skin testing is important as one of an infection prevention countermeasures in the hospital workers.