hematology and oncology
Complications of Transfusion
Delayed hemolytic transfusion reaction
Occasionally, a patient who has been sensitized to an RBC antigen has very low antibody levels and negative pretransfusion tests. After transfusion with RBCs bearing this antigen, a primary or anamnestic response may result (usually in 1 to 4 weeks) and cause a delayed hemolytic transfusion reaction. A delayed hemolytic transfusion reaction usually does not manifest as dramatically as acute hemolytic transfusion reaction. Patients may be asymptomatic or have a slight fever. Rarely, severe symptoms (eg, low-grade fever, jaundice) occur. Usually, only destruction of the transfused RBCs (with the antigen) occurs, resulting in a falling hematocrit and a slight rise in lactate dehydrogenase and bilirubin and a positive direct antiglobulin test. Because delayed hemolytic transfusion reaction is usually mild and self-limited, it is often unidentified, and the clinical clue may be an unexplained drop in hemoglobin to the pretransfusion level occurring 1 to 2 weeks posttransfusion. Severe reactions are treated similarly to acute reactions. 