Comparison of particle concentration fluorescence immunoassay to card and complement fixation tests using isolation of Brucella abortus as the standard.

Serologic test data and bacteriologic culture results from 816 cattle were evaluated. Brucella abortus (field strain or strain 19) was isolated from 27.3% of the cows. Results of the card test, particle concentration fluorescence immunoassay (PCFIA), and complement fixation (CF) test were compared. Antibody titers were directly associated with B. abortus isolation, with the majority (64.7%) of field strain isolations having a PCFIA value of < or = 0.300 and a CF test result of at least 1+ at a 1:160 dilution. The specificity of the CF test was significantly higher than that of the PCFIA (at CF > or = 1:40 and PCFIA < or = 0.300).