Case report: ABO discrepancy due to vancomycin complicating a transfusion reaction investigation

A 3-year-old patient with acute myelogenous leukemia developed fever and chills during transfusion of packed red cells. A preliminary workup suggested that a group AB donor unit had been issued to a Group A patient. However, a discrepancy between the ABO group of the original donor unit segment (A) and blood taken from the IV tubing (AB) and the patient's pre- and posttransfusion samples (A and AB, respectively) suggested another reason for the weak reactivity of some samples with anti-B. The patient's chart revealed that vancomycin, reported to be a cause of non-immune agglutination of red cells, had been injected into the IV tubing one hour prior to transfusion. Further testing confirmed that the patient's febrile response to transfusion was consistent with a nonhemolytic transfusion reaction and was unrelated to the drug-induced, pseudo ABO problem.