Enzyme Linked Immunosorbent Assay versus Polymerase Chain Reaction for diagnosis of brucellosis

The aim of study was to determine the diagnostic value of Polymerase Chain Reaction (PCR and Enzyme Linked Immunosorbent Assay (ELISN) in 37 confirmed cases of brucellosis and 78 healthy controls. The diagnosis of brucellosis was based on a compatible clinical picture plus a positive blood culture and/or an antibody titer of ≥ 1:160 at the serum agglutination test. Controls were asymptomatic individuals with negative blood cultures and no previous history of brucellosis. PCR and ELISA were performed on all samples. PCR was positive in 15 (40.5%) patients and no controls. Mean±SD (range) ELISA IgG levels in patients and controls were 198.9 ± 63.1 (9.7-231.9) IU mL^-1 and 14.6+27.2 (0-145.0) IU mL^-1, respectively (p<0.001). The area under the receiver operating characteristic curve for distinguishing between cases and controls was 0.977. The cutoff point for ELISA results yielding maximal sensitivity plus specificity was 167.35 IU mL^-1. ELISA proved to be a more appropriate diagnostic method than PCR in the series, with sensitivity, specificity, positive predictive value and negative predictive value of 89.2, 100, 100 and 95.1%, respectively.