UNJUSTIFIED DISCARDING OF TRANSFUSIONAL B LOOD DUE TO BRUCELLA ANTIBODIES

Objectives. To compare the slide microagglutination (SMA) test vs a go ld standard test (tube agglutination test: SAT) for the detection of B rucella antibodies in order to evaluate the usefulness of SMA to disca rd transfusion blood units. Design. Prospective, comparative, cross se ctional survey. Setting. City of Leon, State of Guanajuato, an endemic zone of brucellosis. Samples. 48 sera from blood units discarded for transfusion by three blood banks due to Brucella antibodies detected b y SMA and 48 controls of accepted units. Methods. Determination of Bru ce(la antibodies with the SMA and SAT tests. Results. The 48 control s amples were negative with both tests; of the 48 discarded samples, in only seven sera we confirmed a titer greater than or equal to 1:80 by SAT; thus, 41 blood units (85%) may have been improperly rejected beca use the only test used by the blood banks was the SMA. In our hands, t he SMA showed a sensitivity and negative predictive value of 100%, a s pecificity of 81%,and positive predictive value of 29%. Conclusions. T here was a high proportion of improper rejection of blood units for tr ansfusion; Brucella antibodies at any titer detected by SMA should be followed by SAI testing.