For the diagnosis of brucellosis, a small molecular weight fragment (average 22 kD) of the OPS of
B. abortus strain 1119-3 sLPS is labelled with fluorescein isothiocyanate (FITC) and used as the antigen.
This antigen is added to diluted serum or whole blood and a measure of the antibody content is obtained in
about 2 minutes (for serum) or 15 seconds (for blood) after the addition of antigen using a fluorescence
polarisation analyser (Nielsen et al., 1996a; 2005).