Comparison of fluorescence polarization assay with Rose Bengal (RB) test and complement fixation tests for the diagnosis of buffalo (Bubalus bubalis) brucellosis in a high-prevalence area

Abstract

The fluorescence polarisation assay (FPA) was evaluated for the serological diagnosis of bovine brucellosis in buffalo (Bubalus Bubalis) in southern Italy. This assay uses O-polysaccharide prepared from Brucella Abortus lipopolysaccharide conjugated with fluorescein isothiocyanate as a tracer. It has many methodological advantages over older, more established tests and can be performed in short time. To measure the fluorescence polarization, a Tecan GENios Pro (Prionics) fluorescence-polarization analyzer was used with the procedure described by Nielsen et al. 1996. A cut-off value of 117 millipolarization (mP) units was used for testing 912 buffalo sera from Campania Region (526 positive sera and 386 negative sera according to the complement fixation test; CFT). All samples were tested with the Rose Bengal plate (RB). Sensitivity and specificity (Sn) for RB were 84.0% and 87.8% and for FPA were 92.6% and 88.9 percent. The FPA gave a kappa coefficient of agreement with respect to CFT of 0.755, while RB (relative to the CFT) gave coefficients of 0,715. Finally, ROC analysis suggested a cut-off value which did not agree with the one recommended in the test procedure for cow.

Keywords

• Brucellosis
• Bubalus bubalis
• FPA