Prevalence of erythrocyte alloimmunization in polytransfused patients.

Objective: To determine the incidence and the rate of red blood cell alloimmunization in polytransfused patients.

Methods: A polytransfused patient was defined as having received at least 6 units of red cell concentrates during a 3-month period. The records of all patients (n = 12,904) who had received red blood cell units were examined retrospectively by searching the computer database at Hospital Israelita Albert Einstein in São Paulo, Brazil, over a 6-year period, between 2003 and 2009.