The frequency profiles of size of two-step tuberculin skin tests with histories of BCG vaccinations and tuberculin tests among hospital employees

Abstract

In 1998, Prevention Committee of the Japanese Society for Tuberculosis announced guidelines for dealing with nosocomial tuberculosis infections. These guidelines recommended the two-step tuberculin tests (TST) as baseline data for each medical employee when they started to work. If accurate records of previous TSTs are available in addition to baseline data, they are useful to evaluate the presence of tuberculosis infection when they started to work. We therefore studied the frequency profile of size of TST among medical employees in INBA-HITEC Medical Center and discussed methods to improve investigative measures for tuberculosis infection, and prior to skin testing we asked self-reporting questionnaires regarding history of previous BCG vaccinations and TSTs. We expected that their records of previous TSTs were accurately preserved, however, records of previous TSTs reported by medical employees were found to be inaccurate. From two-step TSTs results, the magnitude of booster phenomenon was defined by diameter of erythema and induration. Results demonstrated that the increase of induration size was larger in subjects > or = 41-years-old than in subjects < 41-years-old. Regarding booster phenomenon, no statistically significant differences were detected according to type of duty post. Many subjects with size of TST erythema > or = 30 mm on the first test showed increase erythema > or = 10 mm on the second test. We therefore suggest that the second test be made for those showing reaction size > or = 30 mm on the first test.