Designing and validation of indirect and competitive ELISA for diagnosis of Brucellosis in human

Aims. The purpose of this study was to evaluate the performance of the indirect ELISA (I-ELISA) and competitive ELISA (C-ELISA) for diagnosis of human brucellosis in comparison to routine serological methods. Methods. Brucella abortus S99 used for LPS preparation. LPS extracted by hot phenol method with enzymatic digestion. Microtitre plates coated with LPS. For I-ELISA, binding antibodies to LPS revealed by peroxidase conjugated anti-human IgG1 and for C-ELISA, antibodies revealed by peroxidase conjugated mouse monoclonal antibody M84. Results. The cut off values (obtained by testing negative serum samples) were set at 17.92-21.63% positivity (P%) for I-ELISA and 53.29-56.91% inhibition (I%) for C-ELISA. The specificity for I-ELISA and C -ELISA were 95.5% and 99.5%, respectively. The sensitivity for I-ELISA and C-ELISA were 100% and 96.94%, respectively. The positive predictive value for I-ELISA and C-ELISA were 93.33% and 98.96%, respectively. The negative predictive value for I-ELISA and C-ELISA were 100% and 98.51% and overall agreement were 96.98% and 98.66%, respectively. Conclusion. The results indicate the potential of I-ELISA and C-ELISA as sensitive, specific, rapid and simple methods for diagnosis of human brucellosis.