Evaluation of a new ELISA (Bartels) for detection of Legionella pneumophila antigen in urine

Background. Detection of Legionella pneumophila soluble antigens allows rapid diagnosis of pneumonia caused by these bacteria. A new ELISA (Bartels) for antigenuria detection has recently been commercialized. We compared the new ELISA with another well-established ELISA (Binax). Methods. To evaluate ELISA-Bartels (Legionella Urinary Antigen, Intracel, Issaquah, Washington, United States), urine samples previously characterized by ELISA Binax (Legionelia Urinary Antigen Enzyme Immunoassay Kit, Binax, Portland, Maine, United States) were used. Samples came from Legionella outbreaks (n=48), from sporadic legionellosis (n=38), and from children with viral pneumonia (n=21). Samples from the External Quality Control of Legionella of the European Working Group on Legionella Infections (n=102) were also tested. Of the samples analyzed, 109 were positive in ELISA-Binax, 2 were equivocal and 98 were negative. Samples showing equivocal results were excluded from the analysis. Results. The sensitivity of ELISA-Bartels in comparison with that of ELISA-Binax was 98.2% (107/109) and specificity was 82.7% (81/98). In the 17 samples that were positive in ELISA-Bartels and negative in ELISA-Binax, 10 were positive in ELISA-Binax after concentration by selective ultrafiltration and 6 further cases showed serology indicating or compatible with recent Legionella infection and were thus classified as true positives. Conclusions. ELISA-Bartels showed good sensitivity and specificity. Sensitivity was even higher than that of ELISA-Binax. Thus, we consider it to be an appropriate method for diagnosis of Legionella pneumonia.