Two studies and an editorial published in the journal Transfusion discuss red cell alloimmunization among patients with sickle cell disease and patients with myelodysplastic syndrome, or MDS. Red cell alloimmunization is defined by the development of alloantibodies against donor cell antigens, and may be associated with hemolytic reactions and severe clinical consequences. Although estimates vary, the rate of alloimmunization in the general population is 0.5-1.5%. However, rates among chronically transfused patients are significantly higher.
A recent multicenter study found that 14.4% of sickle cell patients experiencing pain without acute chest syndrome had a history of alloimmunization. Other studies have suggested that sickle cell patients may experience an alloimmunization rate between 8 and 36 percent.
An additional study among transfusion-dependants patients with MDS or chronic myelomonocytic leukemia found that 15% of these patients became alloimmunized, with an incidence rate of 1 alluimmunization event per 10.5 person-years. Antigens from the Rh system and Kell were most commonly responsible for antibody development.
In an accompanying editorial, Drs. Angela Treml and Karen King discussed the implications of alloimmunization rates among these populations. Specifically, they suggested that hospital services should adopt a rational approach to transfusion management among patients at high risk of alloimmunization.
Here is Dr. King:
“Among patients with sickle cell disease, antigen matching protocols have been associated with a reduction in the rate of alloimmunization and a decrease in hemolytic transfusion reactions. Despite this reported success, studies and surveys have demonstrated no consistent standard of care with significant variability in transfusion practice particularly related to the extent of antigen matching for these patients.“
A survey of over one thousand transfusion medicine laboratories in North America found that most labs match only for ABO and D for sickle cell patients who had not previously been alloimmunized. However, other laboratories prophylactically match for the most clinically relevant antigens, which include C, E, and Kell. In addition, some laboratories provide extended phenotypic matched RBC units for these patients.
There is currently no method to predict which patients will develop alloantibodies, making it difficult for transfusion services to determine the most appropriate antigen-matching policy.
Once again, here is Dr. King:
“Taken together, these two papers indicate the need for a rational approach to the transfusion management for all patient groups at high risk for red cell alloimmunization, including patients with sickle cell disease and those with MDS. Until more optimal predictive or preventive measures are available, implementation of relatively broad transfusion protocols is our best approach to prevention of alloimmunization and provision of safe blood in a timely manner for all patients at increased risk.”
We’ll be back on April 30th with another edition of Transfusion News. Thanks for joining us.
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