ABSTRACT
OBJECTIVES: To compare the slide microagglutination (SMA) test vs a gold standard test (tube agglutination test: SAT) for the detection of Brucella antibodies in order to evaluate the usefulness of SMA to discard transfusion blood units. DESIGN: Prospective, comparative, cross sectional 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 by SMA and 48 controls of accepted units. METHODS: Determination of Brucella antibodies with the SMA and SAT tests. RESULTS: The 48 control samples were negative with both tests; of the 48 discarded samples, in only seven sera we confirmed a titer > or = 1:80 by SAT; thus, 41 blood units (85%) may have been improperly rejected because the only test used by the blood banks was the SMA. In our hands, the SMA showed a sensitivity and negative predictive value of 100%, a specificity of 81%, and positive predictive value of 29%. CONCLUSIONS: There was a high proportion of improper rejection of blood units for transfusion; Brucella antibodies at any titer detected by SMA should be followed by SAT testing.
