Acute haemolytic transfusion reactions due to weak antibodies that in vitro did not seem to be clinically significant.

BACKGROUND AND OBJECTIVES: In the present article, we report on two patients with acute haemolytic transfusion reactions (AHTRs), and whom we were unable to transfuse, owing to alloantibodies that in vitro did not seem to be clinically significant., MATERIALS AND METHODS: The patients were a 67-year-old male and a 64-year-old female, both of whom developed antibodies to red blood cells (RBCs) after repeat blood transfusions. Serological analyses were carried out using standard techniques., RESULTS: Both patients developed an AHTR of the intravascular type following blood transfusions. Serological re-examination revealed weakly reactive alloantibodies with anti-JMH specificity in one patient, and with unclear specificity in the second. Rechallenging the patients with 15-30 ml of packed RBCs caused AHTRs, and blood transfusion became impossible in both cases., CONCLUSION: Weak alloantibodies that in vitro do not seem to be clinically significant may cause severe AHTRs.