Comparison of the Novel Immunocatch Legionella Test with Sofia Legionella FIA Assay and with BinaxNOW Legionella Card Assay for Detection of Legionella pneumophila (Serogroup 1) Antigen in Urine Samples

Abstract

Legionnaires' disease (LD) refers to a serious form of acute pneumonia caused by Legionella species. LD can be difficult to diagnose because the signs and symptoms are nonspecific, and therefore a rapid laboratory diagnosis is of paramount importance. In this study, a recently introduced immunochromatographic test (Immunocatch Legionella; Eiken Chemical Co., Ltd.) for Legionella pneumophila (serogroup 1) urinary antigen detection was compared with the Sofia Legionella fluorescent immunoassay (FIA) (Quidel) (routinely used in our laboratory) and with the widely used BinaxNOW Legionella assay (Alere). A total of 248 urine samples (60 frozen and 188 fresh) were evaluated. All of the samples were collected from patients with high clinical suspicion of Legionnaires' disease. The three assays were performed simultaneously according to the manufacturers' instructions. A total of 180 concordant negative and 66 concordant positive results were obtained. Only 2 discrepant results were registered. The sensitivity and specificity of Immunocatch compared with Sofia were, respectively, 98.5% and 99.4%. Cohen's kappa coefficient and overall percent agreement between Immunocatch and Sofia were also calculated and resulted in, respectively, 0.97 and 99.2%. These performances suggest that the Immunocatch test is a useful tool for Legionella pneumophila (serogroup 1) urinary antigen detection.

A Hospital-based Study on the Local Epidemiology of Pneumonia Including the Contribution of Legionella Pneumonia

“…The sensitivity of the ICT assays for both the Immunocatch TM LUAT ICT test and the commercially available competitor, BinaxNOW ® LUAT ICT test (Alere Inc., USA) for the Legionella pneumophila serogroup 1 was 80%, and the specificity was 97% with a 98% overall agreement between the two tests. Comparison between the ICT assays and the urine EIA test showed 98% overall agreement and a specificity of 100% ( 33 – 35 ). This discovery has allowed a five-day reduction for the delay between the onset of illness and notification, as well as facilitated decreasing mortality trends in developed nations.…”