Detection of Legionella pneumophila antigen in urine samples by the BinaxNOW immunochromatographic assay and comparison with both Binax Legionella Urinary Enzyme Immunoassay (EIA) and Biotest Legionella Urin Antigen EIA

Abstract

The new BinaxNOW Immunochromatographic (ICT) Assay for the detection of Legionella pneumophila antigens was used to test 535 urine specimens from patients with and without Legionnaires' disease. The speci®city, calculated by testing 112 samples from patients with pneumonia of aetiologies other than Legionella infection, and 167 urine specimens from urinary tract infections, was found to be 97.1% if the manufacturer's guidelines were followed. However, it was determined that the`false positive' results characterised by very weak bands could be discounted by reexamination of the results at 60 min, yielding a speci®city of 100%. With this minor modi®cation of the procedure applied to examination of urine samples from 117 patients with legionellosis con®rmed by isolation of L. pneumophila and 70 patients who had seroconverted to L. pneumophila serogroup 1, sensitivity was calculated to be 79.7%. In comparison, the sensitivities of the Binax Urinary Antigen Enzyme Immunoassay (EIA) and Biotest Urin Antigen EIA were estimated to be 79.1 and 83.4%, respectively. Eleven cases (5.9%) were positive by BinaxNOW assay but negative by Binax or Biotest EIA, or both. The sensitivities of all assays increased to c. 94% if only diagnosis of cases con®rmed by isolation of serogroup 1 L. pneumophila was considered, although the sensitivity for infections caused by L. pneumophila serogroup 1 monoclonal antibody (MAb) subgroup Bellingham was signi®cantly lower than for other MAb subgroups. The Biotest EIA recognised 10 (45%) of the 22 cases not caused by L. pneumophila serogroup 1, whereas the two Binax kits detected only three each. The ICT assay BinaxNOW can be recommended as a rapid speci®c test for the diagnosis of Legionnaires' diseases caused by L. pneumophila serogroup 1, although very weak bands should be interpreted cautiously.

Comparison of Diagnostic Sensitivities of Three Assays (Bartels Enzyme Immunoassay [EIA], Biotest EIA, and Binax NOW Immunochromatographic Test) for Detection of Legionella pneumophila Serogroup 1 Antigen in Urine

“…By contrast, the Binax NOW ICT was significantly less sensitive than the EIAs, detecting only 37% of the cases. We did not expect to find such a large difference, since previous studies have shown that the sensitivity levels of both tests (the ICT and the EIAs) are approximately the same (8,14). In spite of this, our findings are in agreement with those of Dominguez et al (2), who observed that the sensitivity of the ICT assay using nonconcentrated samples was 55.5% relative to the EIA results; after concentration of the urine, the sensitivity levels of the two methods (EIA and ICT) were the same.…”

“…The differences in sensitivity levels for the three tests were not significant (P ϭ 0.2). Multiple com-parisons of the commercially available kits have been previously published (5,7,8). None of these previous studies were reported to have demonstrated significant differences in the abilities of the different tests to detect L. pneumophila antigen in urine.…”

Clinical and microbiological features of patients admitted to the intensive care unit with nursing and healthcare-associated pneumonia

“…18,19 Streptococcus pneumoniae and Legionella pneumophila serogroup 1 antigens in urine were tested by immunochromatography. 20,21 Causative pathogens of pneumonia met one of the following criteria: sputum Gram stain showing phagocytic cells and bacteria equivalent to 10 3 -10 5 colony-forming units (CFU)/ml in sputum culture; >10 6 CFU/ml bacteria in the sputum culture; blood culture-positive; positive urinary pneumococcal or urinary Legionella antigen-test results; positive antibody titers against M. pneumoniae and C. pneumoniae.…”

Clinical Utility of Urinary Antigen Detection for Diagnosis of Community-Acquired, Travel-Associated, and Nosocomial Legionnaires' Disease

“…However, in routine and clinical laboratory work, legionellosis is rarely proven by culture whereas detection of urinary antigen is now common (6,14). All commercially available assays, except the Biotest enzyme immunoassay (EIA) (Dreieich, Germany), are marketed by their manufacturers as kits for the detection of L. pneumophila serogroup (sg) 1 urinary antigen, but some recent studies have shown that in practice the sensitivities of these assays ranged from 14 to 65% for non-sg 1 infection (1,9,10,12). None of these studies, however, provide information on the clinical utility of urinary antigen detection for the diagnosis of community acquired, travel-associated, and nosocomial Legionnaires' disease with regard to the distribution of serotypes among these categories of infections.…”