Evaluation of Tuberculin Skin Test (TST) in Medical Students in Mazandaran University of Medical Sciences, Sari, Iran

BACKGROUND: Working in health care units has been known as occupational risk factor in mycobacterium tuberculosis (TB) infection. The TB exposure rate in medical students is more than other people. In several studies significant correlation has been reported between hospital presence hours and positive PPD test prevalence. With regard to morbidity of several medical students and nursing staff due to primary tuberculosis in recent years, we decided to investigate positive tuberculin skin test (TST) prevalence in medical students and examine correlation between positive cases prevalence with presence hours in hospitals.

METHODS: This was a cross sectional study and 297 medical students of Mazandaran University of medical sciences were investigated. TST was done with Mantoux method. After 48 hours, injection site induration was measured. Subjects that had induration <10 millimeters were injected again (1-3 weeks later) with same method. (As a booster dose)

RESULTS: 32 cases (10.7%) had positive test at the first phase. Second phase was done on rest 265 persons and 20 cases had positive test. In summation 52 positive cases (17.5%) were observed. 21 cases of 151 persons (13.9%) in group with <100 hours/annual hospital presence, had positive tests. 21 cases of 71 persons (16.9%) in group with 100-1000 h/a hospital presence (Extern) and 19 cases of 75 people (25.3%) those who had >1000 h/a hospital presence(Intern), had positive tests. There was a meaningful statically difference in positive tests, between groups < 1000 hours exposure and the other who had > 1000 hours contact (p=0.032).

CONCLUSIONS: Because of, Interns’ high responsibilities and their more involvement in patient’s diagnostic and therapeutic process, they have high chance to contact with undiagnosed and diagnosed tuberculosis patients. Due to these reasons, TB infection rate is increasing among Interns. As a result of these findings, performing PPD test should be considered at the beginning of entrance to hospital departments and then annually. Necessary tasks and following up are needed to new positive cases.