Initial selection of blood for patients with WAIHA. The algorithm is a suggested approach for the selection of RBC units in patients with WAIHA who are initially evaluated by the transfusion service. Serologic phenotyping of the patient's RBCs and provision of prophylactic antigen-matched RBC units are dependent on the available antisera at the institution and the patient's recent transfusion history. If it is discovered that the patient has a known history of alloantibodies, provide corresponding antigen-negative RBC units unless it would delay transfusion in urgent situations.