Performance assessment of five Legionella urinary antigen tests for Legionella pneumophila and Legionella longbeachae

Legionnaires' disease (LD) is a severe pneumonia caused by Legionella species., with Legionella pneumophila serogroup 1 (SG1) responsible for 70-80% of cases in Europe and the United States. In parts of Asia and the Western Pacific, Legionella longbeachae is also a common cause. Most urinary antigen tests (UATs) target only L. pneumophila SG1, limiting detection of other species. We evaluated the performance of five UATs: BinaxNOW immunochromatographic test (ICT), Sofia FIA, STANDARD F FIA, ImmuView and LIAISON, against the Binax enzyme immunoassay, with culture and polymerase chain reaction (PCR) used where available to confirm the infecting Legionella species. A total of 81 urine samples were tested across all assays, except STANDARD F (n=80). BinaxNOW ICT had the highest sensitivity for L. pneumophila SG1 with 100% specificity. ImmuView showed 100% sensitivity and specificity for L. longbeachae and 92.6% sensitivity for L. pneumophila SG1. In regions where L. longbeachae represents a substantial proportion of Legionella infections, the ImmuView assay offers an effective primary screening approach since it can simultaneously detect both L. pneumophila SG1 and L. longbeachae in a single test, thereby minimising reliance on slower diagnostic methods such as culture or PCR.