Evaluation of the Changes in Tuberculin Skin Test (TST) among the Interns in Isfahan University of Medical Sciences (IUMS), Iran, after One Year of Starting Internship during the Years 2016-2017

Background: Medical students, especially whom enter to clinical courses, are in high exposure of Mycobacterium tuberculosis responsible for tuberculosis (TB). This emphasizes the need to evaluate the condition of exposure to tuberculosis in this population. Methods: In this cross-sectional descriptive study, changes in tuberculin skin test (TST) was evaluated among 140 interns in Isfahan University of Medical Sciences (IUMS), Iran, during the years 2016-2017. Purified protein derivative (PPD) was injected into the medial side of forearm. After 72 hours, the diameter of induration was measured. 10 mm of induration and higher was considered as positive. 1 year later, the tuberculin skin test was repeated. The results from the first and second tuberculin skin tests were compared and analyzed. Demographic information was recorded. Findings: 46.4% of examined population were men. In first tuberculin skin test, 8 cases (5.7%), and in second test, 10 cases (7.1%) were positive. 2 cases of test conversion were found. Mean induration size among all interns was 2.82 and 3.17 mm in first and second tuberculin skin tests, respectively. In both tests, men had significantly more positive results. Conclusion: In this study, 2 test conversion cases were found. As these interns will have more exposure in their educational and professional future, it needs to perform useful plans to control and prevent transmission of tuberculosis.