The Royal Marsden Hospital Manual of Clinical Nursing Procedures - Lisa Dougherty [290]
Hepatitis B virus (HBV)
Screening for hepatitis B surface antigen (HBsAg) in donor blood is mandatory as it is estimated that there are now more than 325,000 people in the UK with chronic hepatitis B and, allowing for factors such as under-reporting, the figure may be even higher (Hepatitis B Foundation UK 2007).
Hepatitis C virus (HCV)
Screening for hepatitis C using the ELISA is mandatory in the UK. Hepatitis C is transmitted primarily via contact with blood or blood products (Friedman 2001).
Human immunodeficiency virus (HIV-1 and HIV-2)
The human immunodeficiency virus is a retrovirus that infects and kills helper T cells, also known as CD4-positive lymphocytes. Transmission of the virus can be via most blood products including red cells, platelets, FFP, and factor VIII and IX concentrates. These viruses are not known to be transmitted in albumin, immunoglobulins or antithrombin III products (Barbara and Contreras 2009). The retrovirus invades cells and slowly destroys the immune system, rendering the individual susceptible to opportunistic infections. Since 1983, when it was recognized that the virus could be transmitted via transfusion, actions have been developed to safeguard blood supplies from transmitting the virus that caused acquired immune deficiency syndrome (AIDS). These include the careful screening of donors and the testing of donated blood.
Other infective agents
Parasites
Plasmodium falciparum is the most dangerous of the human malarial parasites (Barbara and Contreras 2009). Prevention is maintained by questioning donors about foreign travel, in particular those who have visited areas where the disease is prevalent (Bishop 2008).
Prion diseases
Known as transmissible spongiform encephalopathies (TSEs), these are a rare group of conditions which cause progressive neurodegeneration in humans and some animal species (Box 8.4). Prion diseases are believed to be caused by the presence of an abnormal form of a cellular protein (Aguzzi and Collinge 1997, Barbara and Contreras 2009, Vamvakas 1999). These abnormal proteins have an altered cellular shape, and become infectious and multiply by converting normal cellular protein to the irregular form. This irregular form is resistant to digestion and breakdown and, once accumulation occurs, can result in the formation of plaque in brain tissue. Transmission is thought to be by direct contact with infected brain or lymphoreticular tissue (Aguzzi and Collinge 1997, Barbara and Contreras 2009, Vamvakas 1999).
Box 8.4 Prion diseases
Prion diseases in animal species
Scrapie, a disease of sheep.
Bovine spongiform encephalopathy (BSE).
Feline spongiform encephalopathy (FSE).
Chronic wasting disease of deer, mule and elk.
Prion diseases in humans
Sporadic: classic Creutzfeldt–Jakob disease (CJD).
Inherited: CJD, Gerstmann–Sträussler–Scheinker disease, fatal familial insomnia (FFI).
Acquired: kuru, vCJD.
There is evidence to suggest that in TSEs, of which vCJD is one, leucocytes, particularly lymphocytes, are the key cells in the transportation of the putative infectious agent to the brain (Aguzzi and Collinge 1997, Bradley 1999). There were a total of 163 deaths in cases of definite or probable vCJD in the UK up to 31 December 2007. A further three probable cases were alive on 31st December 2007. Analysis of the incidence of vCJD onsets and deaths from January 1994 to December 2007 indicates that a peak has passed. While this is an encouraging finding, the incidence of vCJD may increase again, particularly if different genetic subgroups with longer incubation periods exist (National CJD Surveillance Unit 2008).
In many developed countries, blood undergoes universal leucodepletion for a number of reasons: to reduce the risk of transmission of vCJD, to remove leucocyte-associated viruses such as CMV and to reduce other complications of transfusions related