Reactions due to white cell and platelet antibodies

Febrile transfusion reactions

Febrile reactions are most frequently due to sensitization to white cell antigens and more rarely to platelet antigens. Together with urticaria, these are the most common type of immuno-logical reaction to blood transfusion. Antibodies are directed usually against HLA antigens, or sometimes against granulocyte and platelet-specific antigens; they are stimulated by previous transfusions or pregnancies. Cytokines released from white cells during storage may also be pyrogenic. Characteristically, the onset of the reaction is delayed until 30-90 min after the start of the transfusion (depending upon the strength of antibody and the speed of transfusion). A rise in temperature may be the sole symptom, but the recipient may suffer chills, headache or rigors. There is no associated hypotension, lumbar pain or chest discomfort. These reactions are usually only troublesome rather than dangerous, except in very sick patients or in the presence of very potent lymphocytotoxic HLA antibodies.

The management of a simple, mild febrile transfusion reaction is to slow the rate of transfusion and treat the patient with an antipyretic such as paracetamol. Antihistamines are of no benefit. It is usually not necessary to discontinue the transfusion: more blood is probably wasted by premature termination of a unit due to a simple febrile reaction than for any other reason.

When a patient requiring repeated transfusions has a history of simple febrile reactions, the rate of transfusion should be kept slow and antipyretics should be prescribed prophylactic-ally. If symptoms recur with repeated transfusions, buffy coat-poor red cells and platelets should be tried. If severe symptoms persist, tests for HLA antibodies (lymphocytotoxicity) should be carried out. If these are negative, platelet antibodies should be sought. Patients with troublesome symptoms in whom white cell antibodies have been demonstrated should be given white cell-depleted blood. Modern prestorage leucodepletion filters are highly efficient and can remove more than 98% of the white cells; the specification is that 99% of leucodepleted components should have < 5 X 106 leucocytes. Red cells and platelets should be filtered as soon as possible after collection in the transfusion centre. In the UK, the incidence of febrile transfusion reactions has decreased significantly since the introduction of universal leucodepletion of blood components in 1999.

In countries where there is no universal leucodepletion policy, there is no need to administer white cell-depleted blood prophylactically, except in cases where prevention of sensitization to HLA and leucocyte/platelet antigens is essential (i.e. possible future consideration for bone marrow transplantation, especially in patients with aplastic anaemia).

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