Transfusion Medicine Technical Manual Cross Matching
Human leucocyte antigens (HLA) are polymorphisms in cell surface molecules that distinguish 'self' from 'non-self'. They may also be involved in pathogenesis of certain autosystem autoimmune and infectious diseases. HLA falls into two classes:. HLA class I antigens (A, B and C) are expressed on the majority of tissues and cells including T and B lymphocytes, granulocytes and platelets.
HLA class II antigens (DR, DQ, DPA and DPB) are constitutively expressed on B lymphocytes, monocytes and dendritic cells but can also be detected on activated T lymphocytes and activated granulocytes. It is not clear whether they are also present on activated platelets. Although their main role is to present antigens to T cells, HLA antigens can also be recognised as foreign by the host T cells.
This mechanism is known as allorecognition. People exposed to non-self antigens through pregnancy, transfusion or transplantation, may become alloimmunised and develop antibodies directed against these HLA antigens. A number of techniques to detect HLA antibodies have been described, which include complement-dependent lymphocytotoxicity test (LCT), enzyme-linked immunosorbent assay (ELISA) and flow cytometry.
HLA matched platelets Human leucocyte antigen (HLA) matched platelets may be required in patients who are at risk of developing, or have developed antibodies to HLA antigens. HLA antibodies are implicated in approximately 20% of cases of platelet refractoriness. Platelet refractoriness is the failure to achieve satisfactory responses to platelet transfusions from random donors.
. Understand the process of blood collection and the preparation of blood components and plasma derivatives. Learn which tests must be performed to assure safe transfusion. Learn the specific indications for transfusion of individual blood components and alternatives to allogeneic transfusion. Understand the clinical complications that may arise after transfusion of blood components.
Learn about the collection and use of hematopoietic progenitor cells. Learn the process of apheresis and its clinical indications. Transfusion medicine is the field of medicine that encompasses blood banking (the collection, preparation, testing, and storage of blood components and plasma derivatives) as well as the therapeutic uses of blood components, plasma derivatives, and apheresis technology. It also includes the collection, storage, and use of hematopoietic and other blood-derived cells.
An overview of the steps from collection of the blood to transfusion of its components is shown in. Briefly (with more complete descriptions to follow), blood is collected as whole blood or by apheresis from screened, volunteer donors, and samples of the blood are tested for infectious diseases and to determine the blood type. Whole blood may be fractionated into packed red blood cells (RBCs), platelets, and a plasma product. Alternatively, all 3 components can be collected by apheresis. Plasma can be further processed to provide albumin, clotting factor concentrates, and immunoglobulin preparations. The transfusion of blood components requires testing to be done to establish compatibility between the product and the intended recipient. Blood components may also be treated to reduce complications of transfusion (eg, remove leukocytes to prevent febrile reactions).
As complex, biologically derived therapeutic agents, blood components and derivatives are responsible for a variety of potential untoward effects that must be evaluated and managed. The entire process, from blood collection to transfusion and posttransfusion evaluation, is described in this chapter (see ).
The cornerstone of a safe blood supply is the volunteer blood donor who is motivated by altruism. In the past, the use of paid donors was associated with increased levels of transfusion-transmitted hepatitis. Concerns remain about the impact of significant financial incentives on the frank disclosure of health problems or high-risk behaviors that might disqualify a potential blood donor. In the United States, virtually all of the blood is collected from volunteer donors. Regional blood centers collect and distribute more than 90% of the US blood supply while hospital blood banks collect the remainder.
Transfusion Medicine Technical Manual Cross Matching Procedure
The Food and Drug Administration (FDA) Center for Biologics Evaluation and Research regulates all aspects of blood collection and processing, but most blood banks and donor centers are.