Fluorescence polarization assay for the diagnosis of bovine brucellosis: adaptation to field use

A fluorescence polarization assay (FPA) was used to test whole blood sample s prepared by mixing blood cells from cattle without exposure to Brucella a bortus (B. abortus) with sera from animals with confirmed (bacteriologicall y) infection. A cut-off value between negative and positive values was init ially established to be 87.2 mP. This value was changed to 95 mP to increas e assay specificity without loss of sensitivity when testing blood samples from negative animals. The FPA technology was applied to whole blood sample s in the field and to stored whole blood samples using two diluent buffers. Relative sensitivity and specificity values for the FPA performed in the f ield, based on buffered antigen plate agglutination test and competitive en zyme immunoassay results were 95.3 and 97.3%, respectively However, to obta in maximum sensitivity and specificity, a cut-off value of 105 mP was deter mined for fresh whole blood samples. The relative sensitivity and specifici ty values of the FPA when testing stored whole blood samples were 100% each using a 95 mP cut-off. The usefulness of the FPA for testing whole blood samples in the field was demonstrated. Crown Copyright (C) 2001 Published by Elsevier Science B.V. A ll rights reserved.