The effect of donor white blood cell filtration to prevent donor cell survival in transfused trauma patients

White blood cells are thought to cause many adverse blood transfusion reactions. To remove this potential white blood cell filtration (leucodepletion) was universally introduced in Australia (became standard of care) for all red blood cell units in October 2008. Despite leucodepletion, some white blood cells still remain in each red blood cell unit. These white blood cells have been shown to survive long-term in trauma patients in studies conducted in the United States. This is a phenomenon known as microchimerism. It is still unclear what the consequences are for having these donor cells surviving and it is still unclear which patient groups are most affected. It is thought that microchimerism is more likely to establish in patients who are immunosuppressed when they receive a blood transfusion and is most likely to occur in where large volumes of blood are given. Therefore for this study trauma patients were also analysed to determine whether microchimerism occurs in Australia. These patients are immunosuppressed at the time they receive their blood transfusion and are likely to receive larger volume blood transfusions. To determine whether this phenomenon occurs in Australia, trauma patients will be analysed in 2 groups. A retrospective (look-back) study will analyse a blood sample provided by participants who were transfused with at least one red blood cell unit before leucodepletion was universally introduced and after leucodepletion was universally introduced. Some patients in this part of the study will have received leucodepleted blood some non-leucodepleted blood depending on which year they received their blood transfusion. Filtered blood was not necessarily universal practice for each of these patients. We need to determine the incidence of microchimerism both before and after the filtration was introduced. There will be no other follow-up of these patients after the test sample is provided. The prospective study will analyse current trauma patients who are being transfused with universally leucodepleted blood to determine whether there is a continued incidence of microchimerism, how long it takes to establish within a patient and whether they have specific biomarker changes which influence the establishment of microchimerism. Current practice is to provide leucodepleted blood to all blood transfusion recipients so all participants in this part of the study will have filtered blood. There will be a requirement for samples to be provided every 6 months for a period of 36 months following discharge from the hospital.