Delayed hemolytic transfusion reaction due to anti-Js(a) in an alloimmunized patient with a sickle cell syndrome.

Delayed hemolytic transfusion reactions occur via an anamnestic immune response in patients previously alloimmunized by certain RBC antigens. Conventional pretransfusion antibody screening tests and crossmatches are unable to detect certain antibodies that potentially can cause these reactions because they may be present in low concentrations or have low affinity for their respective antigen or their indicator antigen may be absent from test RBCs. We report the second case of a delayed hemolytic transfusion reaction caused by an undetectable (by routine methods) anti-Js(a) in a patient with a sickle cell syndrome (hemoglobin SC disease) and multiple alloantibodies, in whom retrospective indirect antiglobulin tests enhanced by polyethylene glycol revealed the presence of weakly reactive anti-Js(a).