Tuberculin skin test conversions and occupational exposure risk in US healthcare workers

Abstract

Background

Health care workers (HCWs) undergo occupational tuberculosis (TB) screening at regular intervals. However, the risk of contracting TB at the workplace in a setting with a low background TB incidence is unclear. We aimed to evaluate the risk of tuberculin skin test (TST) conversion and the risk of occupational TB infection among HCWs in such a setting.

Methods

We conducted a retrospective cohort study of employees of a large tertiary medical center in the US Midwest who had undergone TST screening during the study period January 1, 1998 to May 31, 2014.

Results

Among 40,142 HCWs who received a TST test, only 123 converted over 16.4 years. Only 9 (7%) of the converters had a suspected TB exposure at the workplace and none developed active TB. The majority of TST converters (66%) had a negative QuantiFERON ^®-TB test at the time of the conversion.

Conclusions

In one of the largest cohorts of HCWs in a low TB incidence setting, we demonstrated an extremely low risk of occupational TB exposure among TST converters and no resulting active TB cases. In this setting, the approach of testing HCWs at baseline and after TB exposure, rather than at regular intervals, should be considered.