Extravascular hemolytic transfusion reaction
Background
- Delayed immune-mediated destruction of transfused RBCs by recipient antibodies (IgG)
- Occurs 2-10 days after transfusion (delayed hemolytic transfusion reaction, DHTR)
- Caused by anamnestic antibody response: recipient was previously sensitized (prior transfusion, pregnancy) but antibody titer fell below detection at time of crossmatch
- Hemolysis occurs extravascularly in the spleen, liver, and bone marrow (reticuloendothelial system)
- Most common clinically significant antibodies: Kidd (Jk), Rh, Duffy (Fy), Kell
Clinical Features
- Often subclinical or mild
- Unexplained drop in hemoglobin or failure of expected post-transfusion hemoglobin rise
- Low-grade fever
- Mild jaundice (indirect hyperbilirubinemia)
- Dark urine (less common than in intravascular hemolysis)
- Rarely progresses to clinically significant hemolysis
Differential Diagnosis
Transfusion Reaction Types
- Acute
- Delayed
Evaluation
- Positive direct antiglobulin test (DAT/Coombs)
- Elevated indirect bilirubin, LDH
- Decreased haptoglobin
- Positive antibody screen with new alloantibody identified
- Inadequate hemoglobin rise after transfusion
- Reticulocytosis
Management
- Rarely requires specific treatment — usually self-limited
- Notify blood bank immediately for antibody identification
- Future transfusions must be antigen-negative for the identified antibody
- Supportive care; transfuse if clinically indicated (with antigen-negative units)
- Monitor for rare progression to severe hemolysis
Disposition
- May not require admission if hemodynamically stable and hemolysis is mild
- Ensure blood bank notification and updated antibody record
See Also
- Transfusions
- Acute transfusion reaction
- Extravascular hemolytic tranfusion reaction
- Graft-vs-host disease