Clinical assessment of the diagnostic performance of the LIAISON® Legionella urinary antigen assay

: Legionella pneumophila is the primary species responsible for Legionnaires' disease, a severe pneumonia. While culture remains the diagnostic gold standard, its slow turnaround time limits clinical usefulness. Rapid methods like urinary antigen tests can improve timely detection. The LIAISON® Legionella Urinary Antigen test is a new chemiluminescence immunoassay designed to identify soluble antigens of Legionella in urine. This study evaluated its performance compared to existing CE-marked antigen tests. Samples were collected from six external laboratories and analyzed in singlicate using both the LIAISON assay and the corresponding comparison method. The LIAISON test demonstrated equivalent performance to reference assays, showing 100% diagnostic specificity and 97% sensitivity-statistically comparable to the claimed 98%. Notably, four samples showed discrepancies between tests, highlighting the diagnostic complexity of Legionella infections. A receiver operating characteristic (ROC) analysis was also conducted to determine the optimal threshold and confirm the assay's cutoff. Results from the LIAISON test were compared to expected outcomes based on consensus criteria. Overall, findings indicate that the LIAISON® Legionella Urinary Antigen assay provides reliable clinical performance for the qualitative detection of Legionella pneumophila and Legionella longbeachae antigens in urine samples from patients with suspected pneumonia in real-world settings.