Comparison of Different Serological Assays for the Differential Diagnosis of Brucellosis

COMPARISON OF DIFFERENT SEROLOGICAL ASSAYS FOR THE DIFFERENTIAL DIAGNOSIS OF BRUCELLOSIS. Two indirect and two competitive Enzyme-linked immunosorbent assays (I-ELISA102, I-ELISA103, C-ELISA1 and C-ELISA2 respectively) have been evaluated in comparison with traditional test such as Radial Immunodiffusion (RID), Complement Fixation (CF), Rose Bengal Agglutination (RB) and Rivanol agglutination (RV). The sera analysed included 1018 sera obtained from non-vaccinated bovines, 848 sera from brucellosis free herds calf vaccinated with Strain-19, 295 sera obtained from brucellosis free herds adult vaccinated with Strain-19 and 665 sera from Brucella abortus biotype 1 (field strain) infected herds. Cut-off off values calculated by ROC analysis were established for each ELISA. Although all ELISAs fulfilled the requirements for sensitivity and specificity, in our hands C-ELISA2 performed slightly better than the other assays for differentiating infected from vaccinated bovines. The specificity of this test was similar to that of RID assay which is known to have high specificity for differentiating adult vaccinated from infected bovines. The kappa value among the different tests was good and within the limits of reproducibility and performance expected for the different assays. From the different immunoenzymatic assays, the C-ELISA2, which uses LPS as antigen and a monoclonal antibody against the C/Y epitope as competing reagent, seems to be the most promising of the ELISAs and therefor can be recommended for screening a large number of serum samples on a laboratory basis.