Life-saving transfusion in autoimmune hemolytic anemia: a case report and procedure review of the dilution method

A woman with autoimmune hemolytic anemia (AIHA) presented in the emergency department with life-threatening anemia (hemoglobin 3 g/dL). Exaggeration of preexisting chronic anemia to severe anemia after a recent red blood cell (RBC) transfusion led to suspicion of delayed hemolytic transfusion reaction. Given the urgency for transfusion along with a stronger suspicion for coexistence of an alloantibody, the dilution method proposed by Lawrence Petz and George Garratty was used to find an RBC unit for transfusion. An alloantibody with Fy^b specificity was identified, which was masked by the coexistent autoantibody. This method is based on the assumption that the titers of an alloantibody are higher than that of autoantibody. Diluting the autoantibody would reveal the alloantibody and, for this purpose, a serial doubling dilution of serum is performed. This method has an important limitation of missing any alloantibodies with titers less than that of the autoantibody. In spite of this, this method may be of use at a resource-poor setting, where trained personnel and other reagents intended for advanced immunohematology methods are unavailable.