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Blood filtration improves safety of blood transfusions

White blood cells can cause costly complications following transfusions; the US and Germany are joining the list of countries requiring filtration of donor blood to remove them.

By | September 28, 2000

HOUSTON. Every three seconds someone in the world needs a blood transfusion. White blood cells (leukocytes) in donor blood can cause serious medical complications, as many viruses (including cytomegalovirus, Human T-cell Lymphotrophic virus and Epstein-Barr virus) and bacteria (including Yersinia) are harboured in leukocytes. Blood donors are typically screened for only a few of these contaminants.

Leukocytes in transfused blood can also suppress the recipient's immune system. Immunosuppression may lead to multiple organ failure, increased risk of post-surgical infection and diminished prospect of cure for patients with certain malignancies. Refractoriness (resistance) occurs when a patient reacts to leukocytes in donated blood and creates antibodies. This immune response, known as 'alloimmunization', can cause resistance to subsequent platelet transfusions; patients do not respond to the transfusion and so have an increased risk of spontaneous bleeding. Febrile non-hemolytic transfusion reaction is characterised by a 1°C or more rise in body temperature within 24 hours of the transfusion. Flu-like symptoms of chills, shaking and (sometimes) headache and nausea are also present.

Clinical studies indicate that leukocyte reduction by filtration reduces risks of these complications, according to Dr Peter Ganz, chief of the blood and tissues division at Health Canada's bureau of biologics. As a consequence of these studies, hospitals and blood centres in North America and some European countries have been converting to 100% filtered blood. The economics of blood filtration are also compelling. Patients receiving filtered blood typically spend 2–6 fewer days in hospital, require fewer antibiotics and diagnostic tests and spend less time with medical personnel.

In September 1998, the US Food and Drug Administration's Blood Products Advisory Committee (BPAC) unanimously agreed that, "the benefit to risk ratio associated with leukoreduction is sufficiently great to justify routine leukoreduction of all non-leukocyte transfusion blood components …" In the US, about 12 million units of blood are collected each year. Although not legally required to filter all blood products, the US medical community has been acting on the BPAC's recommendation that all donor blood should be filtered to remove leukocytes. Since this recommendation, filtered US donor blood has increased from about 16% to almost 50% of the supply. The American Red Cross, which manages about 45% of the US blood supply, plans to filter all donated blood by the end of 2000.

In a new law coming into effect 1 October 2001, Germany mandated filtration of all whole blood, red blood cells and platelets. Four major centres process about half of Germany's 4.4 million annual blood collections. Although most donor blood is presently unfiltered, Pall Corporation has received a $6 million contract for blood filtration systems from the German Red Cross Transfusion Centre in Lower Saxony. This centre began filtering its approximately 700,000 annual collections last month.

Germany is the ninth European nation and the tenth country to require universal blood filtration as a matter of government policy. Among them are France, Canada, the UK, Norway, Malta, Ireland and Portugal. Thirteen other countries, including the US, Japan and Austria are moving without government mandate to filter all donor blood.

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