Comparison of three Legionella urinary antigen assays during an outbreak of legionellosis in Belgium

During an outbreak of legionellosis in Belgium, urine samples of 32 legionellosis patients were tested with three Legionella urinary antigen assays: the Biotest enzyme immunoassay (EIA) kit, the Binax EIA kit and the Binax NOW Immunochromatographic Test kit. The three tests were concomitantly compared. The test sensitivities on the first urine samples were 65.6% for the Biotest EIA, 50.0% for the Binax EIA and 56.3% for the Binax NOW. Testing of a second urine sample increased the sensitivities to 71.9%, 59.4% and 65.6%, respectively. The differences were not statistically significant. In outbreak settings, testing second samples from patients presenting with symptoms but initially testing negative and/or concentrating urine samples for testing might be valuable additions to the urinary antigen test to increase the sensitivities of the tests.