1999 Volume 73 Issue 8 Pages 766-771
A study was made to clarify to what degree the booster phenomenon was present when the employees in a community hospital in Japan received two-step tuberculin testing(PPD). Of the seventyfive employees, most of all BCG-vaccinated subjects, twenty-three showed strongly positve of more than 30 mm of induration at the first test (PPD/T1), and the remaining fifty-two subjects received a second(PPD/T2)after 2 weeks. The second PPD showed a marked increase in reacitivity, sixteen subjects newly became strongly positive and six of eight who were initially PPD negative(<10 mm)were converted positive, and the mean reaction size changed from 14.7±5.6 mm(PPD/T1)to 31.5 ±15.5 mm(PPD/T2). The degree of boosting, measured by the change in millimeters induration size between PPD/T1 and PPD/T2(PPD/T2-PPD/T1), was correlated with neither the size of PPD/T1 nor the age of the study participants, and was not associated with the difference of the position in the hospital. Thus, we could not explain the factor why such a marked boosting was observed in this study. However, these results indicated that the two-step tuberculin testing is an essential means of distinguishing new tuberculous infection from booster phenomenon. We agree with the current recommendation for routine two-step testing of new emplyees in the hospital.
