Comparative trends of brucellosis serological testing and confirmed brucellosis cases suggest inappropriate prescription habits

Background: Brucellosis is a zoonosis endemic to specific geographical regions. In first line laboratories, diagnosis is made by blood culture or Rose Bengal (RB) serology. Methods: We compare brucellosis testing between 2012-2021 at two university hospitals in Brussels, Belgium with concomitant national confirmed cases and institutional cases. Results: RB testing increased from 30 to 211 tests/year between 2012-2021. A total of fifty-two national brucellosis cases were notified during the study period, of which fifteen cases in Brussels. No trend was noted nationally or regionally. Epidemiological data indicated travel to endemic regions, confirmed by strain testing. Institutional cases all showed symptomatic presentations with positive travel histories. Conclusions: Serologic testing inappropriately increases yearly, while annual imported brucellosis cases remain rare, and have positive travel histories and are symptomatic. We therefore support current recommendations of limiting RB testing to symptomatic patients at risk of exposure, meaning predominantly positive recent travel history.