TRALI is defined by as hypoxia with acute shortness of breath and bilateral pulmonary infiltrates all taking place during or within 6 hours of transfusion. TRALI is easy to confuse with Acute Respiratory Distress Syndrome (ARDS) and so ARD must first be excluded before TRALI is considered. According to reports from the Serious Hazard Of Transfusion (SHOT) group, TRALI is now responsible for more cases of transfusion related mortality than post transfusion infection. TRALI is very rarely caused by plasma poor products such as red blood cells but is instead caused by products such as Fresh Frozen Plasma (FFP), which are plasma rich.
TRALI develops following either transfusion of blood products from donor which contain HLA and/or HNA antibodies that recognise matching antigens in the recipient or transfusion of blood products containing lipids and other biological response modifiers. Both routes are thought to lead to pulmonary neutrophil activation. The leading theory is that TRALI develops after two events. Firstly the underlying patient condition, be that trauma, infection or surgery causes priming of neutrophils. Secondly is the transfusion of blood products causes activation of the primed neutrophils.
When TRALI is suspected, the transfusion must be stopped immediate and oxygen must be administered to the patient. Laboratory investigation can then commence. Lab tests undertaken include HLA class I and II and HNA antibody screening and identification of all implicated donors, starting with all female donors and all transfused male donors. Un-transfused male donors are only tested if the tests of the other donors do not identify an implicated donor. HLA antibody screening and identification is nowadays by the solid phase assays such as Luminex. Anti-HNA antibodies investigations are commonly by the flowcytometric Granulocyte Immunofluorescence Test (GIFT) or the Monoclonal Antibody specific Immobilisation of Granulocyte Antigens (MAIGA).
A diagnosis of TRALI is only confirmed after the patient is HLA class I and II and HNA typed to be certain that they express antigens that match antibodies found in the donor. This would have in the past been additionally confirmed with a HLA and/or HNA crossmatch but this is no longer due to improvements in HLA antibody definition. In addition it is very difficult obtain viable granulocytes from patients. The final step is to remove donors identified as the cause of TRALI from the blood donation panel.
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