Aims A positive urinary antigen test for Legionella spp. (Legionella urinary antigen test; LUAT) allows an early switch from empiric to targeted treatment (TT) in hospitalised, community-acquired pneumonia (CAP) patients. We aimed to evaluate the diagnostic, therapeutic and economic consequences of this frequently used test 7 years after its implementation.

Methods We retrospectively evaluated LUATs performed between 2005 and 2011 in two teaching hospitals. All tests performed in hospitalised CAP patients were used in the economic evaluation and positive tests were included in the treatment evaluation. Data on patient characteristics, admission and outcome were retrieved from the patients’ files. The number of days gained by making a rapid aetiological diagnosis, the number of days TT could be provided and their costs were calculated.

Results Of 4485 LUATs, 2504 (56%) were performed for CAP including 55 (1%) positive tests (€1041/positive test). In 26 (60%) of the 43 included positive tests, LUAT was the only test showing Legionella spp. Subsequently, earlier TT was possible in the remaining cases during 209 cumulative admission days (€274/TT day). LUAT led to detection of Legionella spp. 13 days earlier per case (€203/day) as compared with culture/serology alone.

Conclusions Timely LUAT use in accordance with current guidelines allows early detection and treatment of CAP caused by Legionella spp. at considerable expense.