Comparison and evaluation of four commercial kits relative to an in-house immunofluorescence test for detection of antibodies against Legionella pneumophila

Four commercially available kits from (1) Focus Diagnostics, (2) SERION, (3) Zeus and (4) Vircell for detection of antibodies to Legionella pneumophila were evaluated with panels of sera from patients with proven Legionella infection (n = 81) and/or other bacterial infections (n = 75). An in-house indirect Legionella immunofluorescence antibody test (IF test) was used as reference. All sera from the laboratory-proven Legionella pneumophila cases [culture, urinary antigen test and/or polymerase chain reaction] of Legionella infection were found to be positive by the in-house IF test. The relative sensitivity for Focus Diagnostics, SERION, Zeus and Vircell kits was 81.5, 76.5, 68.8 and 62.5%, respectively, and the false-positive rate was 16.0, 5.6, 29.0 and 2.7%, respectively. The in-house IF test had a false-positive rate of 4.0%. It was found that none of the four commercial kits were as sensitive and specific as the in-house IF test.