Abstract
One of the most important and persistent complications of blood transfusion is red blood cell (RBC) alloimmunization. When a patient is exposed to RBC antigens that differ from their own they can form alloantibodies to these foreign antigens. Blood group antigens are highly conserved and follow ancestral patterns of inheritance that may demonstrate population restriction. Minority populations who require chronic transfusion are at particularly high risk of alloimmunization when the blood donor population does not share the same ancestral background, resulting in exposure to non-self RBC antigens. It is incumbent on blood collectors to support patients with risk factors for alloimmunization as well as patients who have already formed alloantibodies. Increasing utilization of RBC genotyping may represent an opportunity to improve access to RBC units from donors that match the extended RBC phenotype of all possible patients.