Challenges associated with assessment of risk for tuberculosis in a dental school setting

Reported risk among health care workers, related to tuberculosis exposure, motivated us to accurately assess this occupational risk at our College of Dentistry.

Our sample population included all dental students entering their junior (third) year (beginning of maximum patient exposure). Screening for tuberculosis infection, with the standardized Mantoux test (purified protein derivative [PPD]), was conducted by the authors; several variables, previously associated with inaccurate test results in the literature, were controlled for during the study.

Among the study population of 158 students, the PPD conversion rate, as determined by one-step testing, after one academic year was 10.6%. To further investigate factors (other than possible workplace exposure) contributing to PPD conversion in the study population, the authors also examined PPD results from previous employee and student screenings and conducted a retrospective chart review of selected patients registered at the college for the same period.

We found that being born outside of the United States and having previously received bacille Calmette-Guérin vaccine are associated with positive PPD test results. In addition, PPD conversion among the study group may not be associated with occupational exposure at the College but, in fact, may be related to other factors, including community- and hospital-based clinical exposure. Finally, we recommend further research that examines the possible systemic effects of periodic testing with PPD on test subjects.