BACKGROUND: The clinical significance of alloimmunization to RBC antigens in sickle cell patients was analyzed by a retrospective review of the records of pediatric and adult sickle cell patients who received transfusions and who were followed over a 10-year period.
STUDY DESIGN AND METHODS: Charts of pediatric and adult sickle cell patients followed at Schneider Children's Hospital (SCH) and Long Island Jewish Medical Center between 1989 and 1999 were retrieved. Patients followed at SCH were classified as pediatric, regardless of age. Data on transfusion history, alloimmunization, and transfusion reactions from 1990 were retrieved from computerized blood bank records. Transfusion history, development of alloantibodies and autoantibodies, and transfusion reactions were correlated with clinical evidence of hemolysis or other adverse reactions from the charts. All patients received ABO- and Rh-compatible blood transfusions for which a partial or extended antigen match was not performed.
RESULTS: Among pediatric patients, 29 percent developed clinically significant alloantibodies, and 8 percent developed autoantibodies. Seven patients developed delayed hemo- lytic and/or serologic transfusion reactions, two with hyperhemolysis, two with clinical evidence of hemolysis, and three with serologic evidence only. The two patients with hyperhemolysis had received extended antigen-matched RBC transfusions to provide blood compatible with their existing antibodies. Among adult patients, 47.0 percent developed significant alloantibodies, and 9.7 percent developed autoantibodies. Five incidences of delayed hemolytic and/or serologic transfusion reactions occurred, one with hyperhemolysis and four with serologic evidence only.
CONCLUSION: The alloimmunization rate is 29 percent in pediatric and 47 percent in adult sickle cell patients when partial or extended RBC antigen match is not performed. However, the delayed serologic and/or hemolytic transfusion reactions did not result in severe clinical outcome in most instances. The most important adverse event was hyperhemolysis, which may be triggered by a transfusion, but was not prevented by matching for RBC antigens. In most instances, the cause of hyperhemolysis was multifactorial.