R-FACT Study:Risk Factors for Alloimmunization After Red Blood Cell Transfusions

Introduction: Individuals exposed to red blood cell (RBC) alloantigens through transfusion, pregnancy, or transplantation may produce antibodies against the alloantigens expressed by RBCs. Although the incidence of these events is debated and ranges between percentages of 1-6% in single transfused patients and up to 30 % in poly-transfused patients (e.g. sickle cell disease, thalassemia and myelodysplasia), they can pose serious clinical problems such as delayed haemolytic reactions as well as logistic problems e.g. to obtain timely and properly matched transfusion blood for patients in which new alloantibodies are detected.

Rationale: It is known that the risk of a recipient to develop antibodies depends on dose and route of administration and the immunogenicity of the antigen, as well as on genetic or acquired patient-related factors. The latter factors however are ill defined and therefore we hypothesize that the particular clinical conditions (e.g. used medication, concomitant infection, cellular immunity) during which transfusions are given may contribute to the risk of immunization.

Research objective: Examine the association between clinical, environmental and genetic characteristics of the recipient of erythrocyte transfusions and the risk against immunization against erythrocyte alloantigens exposed to during that transfusion episode.

METHODOLOGY Study Design and study population We will perform a retrospective matched case- cohort study at hospitals nationwide from a period January 2005 to December 2011. Large red blood cell using hospitals will be selected as study bases. The study cohort will comprise of consecutive red blood cell transfused patients at the study center.

Cases are defined as first time ever irregular red blood cell antibody formers, with no prior history of red blood cell transfusions and alloimmunization before the study period.