Comparison of two commercial enzyme-linked immunosorbent assays with an immunofluorescence assay for detection of Legionella pneumophila types 1 to 6.
Members of the genus Legionella are characterized as gram-negative, motile, freshwater-dwelling bacteria that were responsible for a pneumonia outbreak among American Legion members in 1976. Because clinicians routinely order serologic testing for Legionella pneumophila serogroups 1 to 6 as a screen for possible L. pneumophila infections, we evaluated the Wampole Laboratories L. pneumophila type 1 to 6 immunoglobulin G (IgG) and IgM combined enzyme-linked immunosorbent assay (ELISA) and the Zeus Scientific L. pneumophila type 1 to 6 IgG-IgM-IgA multispecific combined ELISA systems and compared them to an IgG-specific immunofluorescence assay (IFA) for L. pneumophila serogroups 1 to 6. The Centers for Disease Control and Prevention recommends that the positive titer cutoff for an IFA be 1:256. Regardless of where the positive IFA cutoff titer is placed, however, the sensitivity of both commercial assays was below what would be acceptable for a screening assay. With a 1:256 IFA titer as the positive cutoff, the agreement, sensitivity, and specificity of the Wampole ELISA were 74.6, 21.4, and 98.4%, respectively. The agreement, sensitivity, and specificity of the Zeus ELISA were 72.6, 10.5, and 100.0%, respectively. We recommend that any laboratories attempting to replace an IFA type 1 to 6 screen with an alternative ELISA carefully investigate the sensitivity of the replacement assay.
Malan
Annette K
AK
Associated Regional and University Pathologists Institute for Clinical and Experimental Pathology, Salt Lake City, Utah 84108, USA. malanak@aruplab.com
Martins
Thomas B
TB
Jaskowski
Troy D
TD
Hill
Harry R
HR
Litwin
Christine M
CM
D000907:Antibodies, Bacterial / Q000097:blood*; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005455:Fluorescent Antibody Technique; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood*; D016952:Legionella pneumophila / Q000145:classification* / Q000276:immunology*; D007877:Legionnaires' Disease / Q000453:epidemiology / Q000382:microbiology; D011933:Reagent Kits, Diagnostic; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
D000907:Antibodies, Bacterial; D007074:Immunoglobulin G; D011933:Reagent Kits, Diagnostic