Ten Days After the Transfusion of 2 Units, a Patient

Ten days after the transfusion of 2 units, a patient had a 2 g/dL drop in hemoglobin and was slightly jaundiced. No evidence of bleeding was found. What tests would be helpful in determining whether the patient is experiencing a delayed hemolytic transfusion reaction?

A) Culture the donor unit.
B) Compare pretransfusion and posttransfusion ABO and D typing.
C) Perform hepatitis B surface antigen test.
D) Perform an antibody screen on the posttransfusion sample.