With the reductions in transfusion related infection, Transfusion Related Acute Lung Injury (TRALI) has emerged as one of the leading causes of transfusion related morbidity and mortality according to the latest SHOT report. TRALI is defined by SHOT as acute shortness of breath (dyspnoea) with hypoxia and bilateral pulmonary infiltrates occurring during or within 6 hours of transfusion but which is not due to circulatory overload or other likely causes. The blood components most often implicated in TRALI are plasma rich products such as Fresh Frozen Plasma (FFP). TRALI has however been observed following transfusion with low plasma products such as red blood cells.
TRALI occurs following the transfusion of donor HLA and/or HNA antibodies that recognise matching antigens in the recipient or the transfusion of lipids and other biological response modifiers that accumulate during storage of blood components. These lead to pulmonary neutrophil activation. In the leucodepletion era antibodies in the recipient are not considered to be a likely cause other than for granulocyte transfusion. A two event hypothesis has postulated to explain the neutrophil activation. The first event being the underlying condition of the patients, such as trauma, infection, surgery, resulting in priming of neutrophils. The transfusion of blood products is the second event resulting in activation of the primed neutrophils.
Treatment of suspected cases of TRALI involves immediate cessation of transfusion followed by administration of Oxygen. Laboratory investigations follow, involving HLA class I and II and HNA antibody screening and identification in all implicated donors. Investigations usually start with all female donors and all transfused male donors but may be extended to un-transfused male donors. HLA antibody screening and identification has historically been by cell based techniques such as the complement dependent cytotoxicity (CDC) assay or by cell based flowcytometric assays. Currently however, most HLA antibody testing in the UK is by the solid phase Luminex bead based assays. Anti-HNA antibodies investigations are commonly by the flowcytometric Granulocyte Immunofluorescence Test (GIFT) or the Monoclonal Antibody specific Immobilisation of Granulocyte Antigens (MAIGA) test which uses granulocyte antigen specific monoclonal antibodies to specifically capture granulocyte antigens and is therefore useful for differentiating HNA from HLA antibodies.
Patients are HLA class I and II and HNA typed to establish the present of matching antigens for any antibodies that may be present. Historically HLA and/or HNA crossmatching was also undertaken but this is now rare due to improvements in HLA antibody definition tests and the difficulty of obtaining viable granulocytes from the patients.
Donors identified as the cause of TRALI are removed from the blood donation panel.
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