[Unjustified disposal of transfusion blood because of antibodies against brucella].

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.