What are delayed hemolytic transfusion reactions (DHTRs)?

Updated: Jan 12, 2021
  • Author: S Gerald Sandler, MD, FCAP, FACP; Chief Editor: Emmanuel C Besa, MD  more...
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Delayed hemolytic transfusion reactions (DHTRs) occur in patients who have received transfusions in the past. These patients may have very low antibody titers that are undetectable on pretransfusion testing, so that seemingly compatible units of red blood cells (RBCs) are transfused. Exposure to antigen-positive RBCs then provokes an anamnestic response and increased synthesis of the corresponding antibody. After several days, the antibody titer becomes high enough to hemolyze transfused RBCs. The frequency of DHTRs is estimated to be approximately 1 case per 5400 red cell units transfused.

DHTRs are a potentially life-threatening complication of sickle-cell disease (SCD) treatment. In SCD, DHTRs appear to be an immune process that develop because of differences in erythrocyte antigens between blood donors of European descent and patients of African descent. Hemolysis in DHTR can be severe, because both the transfused and autologous red blood cells may be destroyed (so-called bystander hemolysis); DHTR can evolve into hyperhemolysis syndrome Most episodes lead to insufficient reticulocytosis or even profound reticulopenia. [5, 6]

For patient education information, see the Blood Transfusions Directory and Blood in the Urine.

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