Comparison of the results of card, rivanol, complement-fixation, and milk ring tests with the isolation rate of Brucella abortus from cattle.

Specimens from 4,553 cows were examined by card, Rivanol, and complement-fixation (CF) tests and bacteriologic culture. A ring test was performed on milk from 1,003 of these cows. The isolation rate of Brucella abortus correlated directly with antibody titers, and the field strain predominated in adult-vaccinated cows when the Rivanol test titer was greater than + 100 and the CF test titer was greater than 4 + 40. The CF test had the best balance of sensitivity and specificity in adult-vaccinated cows. The false-negative rate for the Rivanol and CF tests was higher in nonadult-vaccinated cows.