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19 - Processing and components: leucodepletion and pathogen reduction
- from Section 2 - Selection and testing
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- By Rebecca Cardigan, Head of Components Development, NHS Blood and Transplant Cambridge, Cambridge, UK, Chris Prowse, Research Director, National Science Laboratory, Scottish National Blood Transfusion Service, Edinburgh, UK, Lorna M. Williamson, Reader in Transfusion Medicine, University of Cambridge; Medical Director, NHS Blood and Transplant, Cambridge, UK
- Edited by John A. J. Barbara, University of the West of England, Bristol, Fiona A. M. Regan, Marcela Contreras, University of the West of England, Bristol
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- Book:
- Transfusion Microbiology
- Published online:
- 12 January 2010
- Print publication:
- 24 April 2008, pp 239-258
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Summary
Although donor selection and donation screening remain the critical elements of protection from transfusion-transmitted pathogens, there is increasing interest in achieving further safety enhancements by component modification. In the last five years, leucocyte depletion has moved from being a bedside procedure for specific patients to a universal and integral part of component processing. In this context, its potential for removal of leucocyte-associated viruses has been the subject of considerable debate. Over the same time period, techniques for pathogen reduction of fresh frozen plasma and platelets have been developed and, in some cases, licensed for routine use. Pathogen reduction for red cells is proving a more challenging prospect, but in time the current difficulties may be overcome. Such techniques present policy-makers with interesting decisions which must take into account cost-effectiveness, loss of functionality of components, potential toxicity, and the potential impact on current donor selection and screening policies.
Leucocyte depletion (LD)
Many countries now undertake universal LD of all components in blood centres within 1–2 days of collection. The reasons for this practice vary from country to country, but perceived benefits include reduced immunomodulation, fewer febrile reactions, and reduction of cytomegalovirus risk (reviewed in Williamson, 2000). In the UK, the main reason for implementation of universal LD was as a precaution against transmission of variant Creutzfeld-Jacob disease. Leucocyte depletion is achieved either by filtration of either whole blood or processed components, or by centrifugation/elutriation during platelet apheresis.
4 - Epidemiology and screening for alloimmune thrombocytopenia
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- By Lorna M Williamson, National Blood Service and University of Cambridge, Cambridge, UK, Michael F Murphy, National Blood Service and University of Oxford, Oxford, UK
- Edited by Andrew Hadley, University of Bristol, Peter Soothill, University of Bristol
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- Book:
- Alloimmune Disorders of Pregnancy
- Published online:
- 26 October 2009
- Print publication:
- 06 December 2001, pp 61-72
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Summary
Background
Alloimmune thrombocytopenia is the commonest cause of severe neonatal thrombocytopenia. The pathophysiology and diagnosis of the disorder are described elsewhere (Sections 1.1.3, 1.3.3 and Chapter 12). Most cases are diagnosed after birth, hence the commonly used term neonatal alloimmune thrombocytopenia. However, there may be severe effects on the fetus in utero, and this, as well as the aetiology, may be emphasized through the use of the alternative term, alloimmune thrombocytopenia. In contrast to HDFN, alloimmune thrombocytopenia frequently occurs in first pregnancies.
Considerable progress has been made in laboratory aspects of platelet immunology since alloimmune thrombocytopenia was first recognized in the 1950s, allowing more precise diagnosis of the condition (Section 12.4) There have also been advances in fetal and transfusion medicine resulting in improvements in its management, particularly in the antenatal management of women with a previous history of pregnancies affected by alloimmune thrombocytopenia (Section 14.3). These advances in laboratory diagnosis and antenatal management have drawn attention to the fact that the first affected fetus/neonate in a family is only recognized after bleeding has occurred, and this has raised the question of screening for alloimmune thrombocytopenia.
The purpose of this chapter is to review the epidemiology of alloimmune thrombocytopenia and then to consider the case for antenatal screening against the criteria for screening programmes set by the UK's Department of Health National Screening Committee. Finally, areas where knowledge is still lacking, and where research effort should be directed, will be highlighted.