Comparison of four commercial IgM and IgG ELISA kits for diagnosing brucellosis

Brucellosis is a worldwide zoonotic disease that often requires serology for diagnosis. The serum agglutination test is the gold standard assay, but ELISAs are used by many laboratories. Many commercial ELISAs are available, but few studies have compared their performance. This study compared the ability of four commercially available ELISA kits (from Bio-Quant, Immuno-Biological Laboratories - America, Vircell and Euroimmun) to diagnose brucellosis in patients from Egypt and the USA. The sensitivities for all kits tested, except the Vircell kit, were >90%, whilst the specificities were variable, with the Bio-Quant assay having a specificity of <40%. Detection of IgG antibody was more sensitive than detection of IgM antibody for diagnosing brucellosis cases, but the specificity was comparable. Overall, there was good agreement between all of the kits except for the Bio-Quant kit. None of the diagnostic assays was 100% reliable for diagnosing brucellosis; therefore, serology results need to be considered in tandem with patient history, clinical signs and other test results.