The LIAISON® Legionella Urinary Ag assay: A novel high-throughput, fully automated dual-antigen detection method with improved sensitivity and expanded Legionella species and serogroup coverage

BACKGROUND: Legionella pneumophila is a leading cause of Legionnaires' disease, with Legionella pneumophila serogroup 1 (Lp1) being the most commonly detected strain. Current urinary antigen tests (UAT) primarily target Lp1, leading to underdiagnosis of non-Lp1 and other Legionella species. A broad-spectrum, fully automated UAT is needed to improve diagnostic accuracy and patient outcomes. METHODS: A novel chemiluminescence immunoassay-based UAT was developed targeting both Legionella peptidoglycan-associated lipoprotein (PAL) and soluble lipopolysaccharide antigen to enable broader detection. Monoclonal antibodies were generated against PAL and integrated into an automated immunoassay platform. The assay's analytical performance was evaluated using recombinant PAL antigens, urine samples spiked with Legionella strains, and clinical specimens. Sensitivity, specificity, cross-reactivity, interference, and precision were assessed. RESULTS: The LIAISON® Legionella Urinary Ag assay demonstrated a 97.5 % positive agreement and 100 % negative agreement with the Binax™ UAT in detecting Legionella infections. Importantly, the new test also identified multiple non-Lp1 Legionella species, which the comparator assay failed to detect. The assay showed low imprecision, no cross-reactivity or interference. CONCLUSIONS: The LIAISON® Legionella Urinary Ag Assay, a fully automated chemiluminescence-based UAT, provides highly sensitive and specific detection of Legionella infections, including non-Lp1 strains, addressing a major limitation of existing diagnostics. This assay has the potential to improve early detection, guide targeted antibiotic therapy, and enhance public health surveillance of Legionnaires' disease.