An overview of red blood cell and platelet alloimmunisation in transfusion

Post-transfusion alloimmunisation is the main complication of all those observed after one or more transfusion episodes. Alloimmunisation is observed after the transfusion of red blood cell concentrates but also of platelet concentrates. Besides alloimmunisation due to antigens carried almost exclusively by red blood cells such as those of the Rhesus-Kell system, alloimmunisation often raises against HLA antigens; the main responsibility for that, apart from platelet transfusions, lies with residual leukocytes in the products transfused, hence the central importance of effective leukoreduction right from the blood product preparation stage. Alloimmunization is not restricted to transfusion, but it is also observed during pregnancies, carrying out microtransfusions of blood from the fetus immunizing the mother through the placenta (in a retrograde way). Preexisting maternal-fetal immunization can complicate a transfusion program and intensify the creation of alloantibodies in several blood and tissue group systems. The occurrence of autoantibodies, created by several pathogenic reasons, can also interfere with the propensity of certain recipients of blood components to produce alloantibodies. The genetic condition of individuals is in fact strongly linked to the ability or not to recognize antigenic variants foreign to their own biological program and mount an alloimmune response. Some hemoglobin diseases, in carriers of which transfusions can be iterative and lifelong, are complicated by frequent alloimmunizations and amplification of the complications of these alloimmunizations, imposing even stricter transfusion rules. This review details the mechanisms favoring the occurrence of alloimmunization and the immunological principles for the production of molecular and cellular tools for alloimmunization. It concludes with the main preventive measures available to limit the occurrence of these frequent complications of varying severity but sometimes severe.     

Platelet component transfusion and alloimmunization: Where do we stand?

Platelet transfusion in patients, particularly in onco-haematology, is frequent and can become chronic in some cases. Post-transfusion alloimmunization is often seen, in practice. The risk of this is significantly improved in multitransfused patients. Several classes of antigens binding on platelets (HLA and HPA) are involved and also red blood cell antigens (residual red blood cells in platelet concentrates). Platelet alloimmunization causes a poor transfusion response, refractoriness and, more rarely, post-transfusion purpura. In an alloimmunized recipient, the efficiency of platelet transfusion is based on the selection of compatible products. Significant technical progress means that several methods are currently available to ensure a good post-transfusion platelet count and a satisfactory clinical outcome for the patient.     

La transfusion du drépanocytaire

Sickle cell disease is a hereditary pathology of the haemoglobin which affects only individuals from African ancestry. The frequency of the disease increases in France. Transfusion remains a major treatment of this disease. Depending of the indication, transfusion can be a simple transfusion or an exchange transfusion. In this last case, exchange can be performed manually or automatically. The transfusion protocols have to be adapted to the polytransfused status of these patients, but also to the high incidence of alloimmunisation against red blood cells. Alloimmunisation is a consequence of the polymorphism of blood groups between sickle cell disease patients and donors of European ancestry. Axes to optimize transfusion safety in these patients have to be developed. But the first step relies on the promotion of blood donation within individuals of African ancestry.     

Transfusion protocols in hematopoietic stem cell allogeneic transplantation]

Hematopoietic stem cell (HSC) allogeneic transplantation is now commonly used as a therapeutic tool in patients with certain types of hematologic malignancies. Such patients, on account of severe pre-graft conditioning regimens, present with severe marrow aplasia justifying specific transfusion care. Given a complex immunological situation (immediately after transplantation, co-existence of two cell populations with different immunohematological characteristics), transfusion protocols must rest on clear and well-defined recommendations. Recent transfusion recommendations in settings of HSC allogeneic transplantation have defined criteria for the choice of blood products (red blood cell concentrates, plasma and platelet concentrates) depending on recipient and graft immunohematological characteristics (minor/major/mixed ABO compatibility/incompatibility and time of transplantation). Transfusion instructions are summarized in a synthesis document entitled : "Instructions for transfusion following HSC allogeneic transplantation". This document specifies the immunohematological characteristics of blood products and various transfusion protocols (systematic irradiation, negative CMV, etc.). This document is used by the teams who distribute blood products, for selection purposes, as well as by the medical transfusion team when they perform ultimate pre-transfusion control steps.     

Transfusional record and blood grouping methods: essential factors of transfusion safety]

The clinical and biological control of the whole transfusion process is a major preoccupation for everyone dealing with blood transfusion. Specially when the patient is a female recipient or belongs to a group with a high prevalence of alloimmunisation. This case report points out the outstanding importance of the immune compatibility, which must be strongly maintained to prevent any harmful consequences. The transfusional record transmission and a simple and sensitive blood grouping test are essential to increase transfusion safety.     

Where will pathogen inactivation have the greatest impact?

Blood safety has always been a major task in transfusion medicine. A strategy to obtain this aim should include donor education, donor selection, and testing of blood donations. Pathogen inactivation adds another level of safety. In the fractionation industry, pathogen inactivation methods are mandatory. Several countries also use pathogen‐inactivated plasma – from pools or single donors. Concerning the cellular blood components, there is still no method available for red cell concentrates, whereas methods for platelet concentrates are available in some countries and others are in the pipeline for commercialization. The efficiency of the ‘old’ methods to increase blood safety and the costs of the methods seem to be major obstacles for the introduction of the systems. There are also concerns on product quality and loss of volume during the inactivation process. As the importance of pathogen inactivation is largest in countries with blood donors who carry infections it is impossible to protect against, either due to high incidence of the infection or due to shortage of tests, cost will be a major question when pathogen inactivation is considered. Pathogen inactivation of red cell concentrates will also be a necessity. When pathogen inactivation methods are available for all blood components, they will have great impact to protect the patients in countries where a high percentage of the population is infected by agents transmissible through blood transfusion, and in all situations to protect against new pathogens and ‘old’ pathogens that become more virulent. The total risk of contracting infectious diseases through blood transfusion will probably be important when implementation of new methods for pathogen inactivation is considered.     

Inactivation of infectious pathogens in labile blood components: meeting the challenge.

Substantial improvement in the safety of blood transfusion has been achieved through the addition of new tests, such as nucleic acid tests, yet residual risk associated with transfusion of blood components persists. Transfusion of blood components has been implicated in the transmission of viruses, bacteria, and protozoa. While it is commonly recognized that hepatitis B virus (HBV), hepatitis C virus (HCV), cytomegalovirus (CMV), and the retroviruses, such as human immunodeficiency virus (HIV) and the human lymphotrophic viruses (HTLV) can be transmitted through cellular components, other pathogens are emerging as potentially significant transfusion-associated infectious agents. For example, transmission of protozoan infections due to trypanosomes and babesia have been reported. In addition to viral and protozoal infectious agents, bacterial contamination of platelet and red cell concentrates continues to be reported; and may be an under-reported transfusion complication. More importantly, new infectious agents may periodically enter the donor population before they can be definitively identified and tested for to maintain consistent safety of the blood supply. The paradigm for this possibility is the HIV pandemic, which erupted in 1979. During the past decade a number of methods to inactivate infectious pathogens in labile blood components have been developed and have entered the advanced clinical trial phase.     

Laboratory hemostatic abnormalities in massively transfused patients given red blood cells and crystalloid.

Most of the literature on massive transfusion concerns whole blood replacement, whereas clinically, packed red blood cells are commonly given. To determine when hemostatic abnormalities occur in patients resuscitated primarily with packed red blood cells and crystalloid, the cases of 39 consecutive patients who were transfused with 10 or more red blood cell units of any kind within 24 hours were reviewed. After transfusion with 20 or more units of red blood cell products of any kind (packed red blood cells, cell-saver units, or whole blood), 75% (3 of 4) of patients had platelet counts less than 50 x 10(9)/L, compared to 0 of 29 patients given less than 20 units (P less than 0.001). After transfusion of 12 units of relatively plasma-free red blood cell products (packed red blood cells or cell-saver units), 100% (8 of 8) of patients had prothrombin time prolonged by more than 1.5 times mid-range of normal, compared to 36% (5 of 14) of patients given less than 12 units (P = 0.012). These data confirm that patients massively transfused with red blood cells of any kind develop significant thrombocytopenia after 20 units. Importantly, probably clinically significant prothrombin time and partial thromboplastin time prolongations occurred consistently after transfusion of 12 units of relatively plasma-free red blood cells in unselected patients at an urban trauma hospital. These data suggest that coagulation factor replacement is necessary in patients who receive 12 or more units of packed red blood cells or cell-saver blood, and platelet replacement is necessary in patients who receive 20 or more units of any red blood cell product. A prospective study is needed to determine whether the expected abnormal clinical bleeding indeed occurs in patients with such laboratory coagulation abnormalities and to determine when plasma transfusion is indicated in patients massively transfused with red blood cells.     

Cryopreservation of red blood cells: effect of freezing on red cell quality and residual lymphocyte immunogenicity.

AIMS--To investigate treatment with glycerol/washing as a potential substitute for freeze-thawing in the production of leucocyte depleted red cell concentrates for patients with a history of non-haemolytic reactions following transfusion. METHODS--The standard procedure of treatment with glycerol/-80 degrees C freezing/thawing/washing was compared with a similar procedure in which freezing was omitted. The quality of the resulting red cell products was assessed in relation to: (1) standard red cell biochemical parameters; (2) leucocyte and lymphocyte subset composition using flow cytometry with fluorescent labelled monoclonal antibodies; and (3) immunogenicity of the residual lymphocytes in mixed lymphocyte culture. RESULTS--Compared with red cells subjected to the standard freeze-thaw technique, red cells undergoing the non-freezing procedure and suspended in additive solutions had significantly better biochemical preservation after 21 days of storage (p < 0.001). Both procedures removed an average 98% of the initial leucocytes at the expense of 18-20% of the red cells. The non-freezing procedure resulted in higher residual concentrations of HLA class II bearing lymphocytes (p < 0.01), but not higher numbers of dendritic cells. Both procedures were equally effective in annulling the residual lymphocytes'' ability to act as stimulator cells in one-way mixed lymphocyte culture. CONCLUSIONS--The non-freezing procedure produces a superior product for the provision of red cells to patients with granulocyte antibodies. These products may also offer a lower risk of HLA alloimmunisation to previously unexposed patients.     

Inactivation des pathogènes des concentrés plaquettaires : expérience française

The transfusion of platelet concentrates is increasing in oncohematology patients due to chemotherapy and hematopoietic stem cell grafts. The transmission of pathogenic agents, viruses, parasites and especially bacteria with platelet concentrates stored at room temperature (20–24 °C) is associated with a septic risk, partly prevented by bacterial detection. Photochemical inactivation of platelet concentrates, using a technique associating amotosalen and UVA, has been used for five years in a French region for the whole population and a large spectrum of patients, with efficacy and safety. Universal implementation of pathogen inactivation in labile blood products is a major and key step to improve safety against infection in transfusion.     

Apheresis versus whole-blood-derived platelets: pros and cons

Platelet concentrates for prophylactic or therapeutic treatment of patients can be isolated from whole blood using the platelet-rich plasma-method or the buffy coat-method on one hand, or can be collected by apheresis with return of unwanted blood cells to the donor on the other hand. A number of variables among the methods, including the anticoagulant, centrifugation and processing after collection, and pre- or post storage pooling, affect storage characteristics of platelets. Data suggest, however, that most differences balance out, both based on in vitro studies, and on recovery and survival studies. A marginal difference in corrected count increment in favor of apheresis platelets was observed, but the practical consequence is likely to be small. The need for pooling of whole-blood-derived platelet concentrates increases donor exposure, and thereby potentially increases the risks associated with transfusion of whole-blood-derived platelet concentrates. Indeed, risk of viral and variant Creutzfeldt-Jakob disease transmission is at least two-fold higher for whole-blood-derived platelet concentrates, but allo immunization rates, acute reaction rates, and transfusion related acute lung injury rates are not different. Apheresis donation procedures have fewer adverse events. The various benefits and disadvantages of the methods have to be balanced when choosing a preferred way of platelet collection.     

Prospects in blood transfusion]

What will be the evolution of blood transfusion in the next 10 years? What are the scientific and medical arguments to help the decision makers to propose the developments? Many scientific and clinical studies show that blood substitutes are not ready for use in man. So, for a long time, blood collection in man will still be a necessity to prepare cell concentrates (red blood cells and platelets) and fresh frozen plasma. During this period, blood safety will be based on development of testing technics and preparation processes of blood products. Another major point will be a better clinical use of blood derivates. Cellular therapy will be probably only a way of diversification in blood transfusion centers in partnership with hospitals.     

Use of a solid phase red blood cell adherence method for pretransfusion platelet compatibility testing

A solid phase red blood cell adherence method has been used for platelet antibody detection and crossmatching for refractory platelet recipients. Patient sera were first screened for HLA or platelet-specific antibodies, then crossmatched with potential apheresis platelet donors. The overall correlation of platelet crossmatch results with transfusion outcome was 97% in patients with no evidence of nonimmune platelet destruction. The solid phase red blood cell adherence method provided a feasible and effective alternative to HLA matching as a means of donor selection for refractory platelet recipients. The speed and simplicity of this method may allow most hospital laboratories to perform platelet antibody screening before routine platelet transfusions.     

Transfusion de plaquettes : produits,indications, dose,seuil, efficacité

The quality of platelet concentrates had been greatly improved since the implementation of processing techniques based on the use of the buffy-coat in the years 1980. More recently, in the last 10 years, it is in the domain of safety that the greatest advances have been done, by the introduction of platelet additive solutions, on one hand, and by the progressive availability of pathogen reduction techniques, on the other hand. These developments in quality and safety of platelet components are important, as they lead to the conclusion that nowadays, apheresis platelet concentrates and pooled random donor platelet concentrates can be considered as equivalent, the only specific indication of the former being the care of HLA or HPA allo-immunized patients. This review covers the physiological basis of prophylactic and curative platelet transfusions, and the means to evaluate their efficacy. The main investigations that are necessary to perform in the event of an inefficient prophylactic transfusion are also mentioned. Platelet transfusion is an essential part of the transfusion support in case of central thrombocytopenia, and more indications in other medical and surgical situations are well defined. The vast majority of clinical situations in which platelet transfusions are indicated have been defined in the national guidelines published in 2003 by the AFSSAPS French authority, and are still fully valid today. Therefore, only some specific domains for which recent published data are questioning our present practices are discussed, such as the use of platelet concentrates in massive transfusion. Finally, three critical factors for establishing a coherent platelet transfusion strategy are developed: the transfusion trigger for prophylactic platelet transfusion, the platelet dose, and the impact of ABO compatibility between the product and the recipient.     

Indications for transfusions of labile blood products]

Indications for transfusions of red blood cells (RBC) are anemias, which can occur after trauma, in surgery, in obstetrics or oncohematology wards. The main criteria to administer RBC transfusion are hemoglobin level and clinical features. Transfusions are rare when the hemoglobin level is above 10 g/dL and are frequent when it is below 6 g/dL. However clinical setting, patient age, associated diseases, cardiovascular complications are taken into account. Immunocompatibility should always be tested and the transfusion consequences checked immediately and on the long term. Platelet transfusions are performed when the platelet count is low and patients suffered from hemorrhage. In oncohematology patients, platelet transfusion are administered with prophylaxis when the platelet count is lower than 10 g/L. Fresh frozen plasma has now a limited use, only in complex haemostatic disorders and in hemolytic uremic syndrome.     

输血支持在造血干细胞移植中的应用

背景：接受造血干细胞移植的患者经常需要血液制品输注支持,而患者对红细胞和血小板输注的需求差异非常大,这主要依赖于造血干细胞移植的类型和患者本身的疾病性质。 目的：评价中山大学附属中山医院接受造血干细胞移植患者移植期间输血的需求和数量。 方法：收集中山大学附属中山医院2004-01/2010-06接受造血干细胞移植患者的资料,包括移植的适应证、移植的类型、CD34+细胞的数量、红细胞和血小板的输注数量、费用、脱离输注时间以及中性粒细胞和血小板植入时间;红细胞输注的阈值是血红蛋白计数为70 g/L,而血小板的输注阈值是计数为20×10⁹ L^-1。研究分析了患者移植期间红细胞和血小板输注的需求、输注量、输血费用,以及患者的生存情况。 结果与结论：自体造血干细胞移植组中有14例(93%)患者,而异基因造血干细胞移植组中有35例(90%)患者显示了造血细胞植入和脱离输注证据。自体造血干细胞移植组取得脱离红细胞输注天数为14.6 d,明显短于异基因造血干细胞移植组。与异基因造血干细胞移植组比较,自体造血干细胞移植组红细胞输注单位明显减少;而异基因造血干细胞移植组的红细胞输注费用明显高于自体造血干细胞移植组。输血花费昂贵,但却是造血干细胞移植中必不可少的一部分,异基因造血干细胞移植组需要更多的输血支持。脱离输注时间有望成为评估造血干细胞移植成功的指标。     

Physiopathological basis of sickle cell disease, management and current therapeutics

Physiopathological knowledge in the area of sickle cell disease underwent a first major development three decades ago, some 15 years after the discovery of the molecular nature of the disease. Several physiopathological areas can be distinguished: physiopathology of polymerisation which has been successfully approached by fundamental biophysicists and biochemists alike; physiopathology of the red blood cell; more recently, the characterisation of red blood sickle cells by extra-hemoglobin aspects: the red blood cell is not a passive recipient for hemoglobin but carries out a series of functions which can contribute to physiopathology; the phenomenon of vaso-obstruction is still poorly understood, whereas clinical secondary manifestations of the disease, the physiopathology of infectious risk and severe anaemic manifestations have been well understood. The treatment of sickle cell patients continues to evolve and progress. There are certain characteristics which remain, however, permanent: there is continual interaction between preventive and therapeutic measures; treatment must be both medical and social, given the impact of the disease of the individual and his family or vice-versa; treatment is centred around the hospital with more than ever the necessity to ensure excellence in internal medicine or paediatrics, intensive care and transfusion. Finally, the distinction among three periods for the natural history of the disease remain: before 7 years of age, from 7 years to adult age, adulthood. An integrated, pilot centre for treating patients with sickle cell disease is of crucial importance and can contribute to therapeutic innovations in the area.     

Immunoprophylaxis using intravenous Rh immune globulin should be standard practice when selected D-negative patients are transfused with D-positive random donor platelets

A 67-year-old female developed excessive bleeding and thrombocytopenia following cardiovascular surgery. Her blood type was group A, D-. The only platelet products available in the transfusion service were random donor platelet concentrates from D+ donors. She was transfused with a pool of 6 D+ random donor platelet concentrates. Anti-D undetected in her pretransfusion serum by solid-phase antibody screen was present 11 days later. Retrospectively, the patient provided a history of having two pregnancies more than 40 years ago, prior to the availability of immunoprophylaxis by Rh immune globulin (RhIG). Although studies have shown that as many as 19 percent of D- people may develop anti-D following transfusion of platelets from D+ donors, there is no specific standard requiring immunoprophylaxis with RhIG to prevent Rh alloimmunization after transfusion of random donor platelet concentrates from D+ donors. In contrast, vigorous efforts are routine for preventing Rh alloimmunization in D- patients requiring red cell transfusions or D- females during pregnancy or after delivery of D+ newborns. The absence of a comparable practice standard for platelet transfusions is based, in part, on concern that intramuscular injections of conventional RhIG may cause local hemorrhage in thrombocytopenic persons. The recent availability of a Food and Drug Administration-approved preparation of intravenous RhIG makes Rh immunoprophylaxis in thrombocytopenic patients safe and practical. We recommend that intravenous RhIG be considered if it is necessary to transfuse random donor platelet concentrates from D+ donors to D- recipients. As a minimal standard, intravenous RhIG should be administered to all D- females of childbearing age who are recipients of pools of random donor platelet concentrates from D+ donors.     

Platelet transfusion practice during dengue fever epidemic

Blood components especially platelet concentrates due to their short shelf life are frequently in limited supply. Appropriate use of blood components is required to ensure their availability for needy patients as well as to avoid the unnecessary risk of transfusion-transmitted diseases. Medical audit of blood transfusion practice, which forms an important part of quality assurance programme in a transfusion centre, can provide grounds for improvement in transfusion medicine practice. During the epidemic of dengue fever in Oct., 1996, 1837 patients were admitted as dengue haemorrhagic fever in a teaching hospital in Delhi. Two hundred and eight patients (11.3%) were given platelet transfusions. Retrospective analysis of these platelet transfusions was done. It was observed that in only 52 (25%) out of 208 patients the information on platelet counts was provided. History of active bleeding was obtained only in 65 (31.2%) patients. About 35% patients received unnecessary prophylactic transfusions and during 89% of the transfusion episodes inappropriate dose of platelet concentrate was given. Information regarding post-transfusion recovery could be obtained in only 16.5% of transfusion episodes. The study emphasises the need for development of specific guidelines for transfusion of blood components, constant interaction and co-ordination amongst clinicians and transfusion centre for implementation of these guidelines, and a regular medical audit to review the optimal utilisation of blood components.     

Erreurs de destinataire de concentrés de globules rouges : méthode d’analyse à partir de déclarations d’incidents de la chaîne transfusionnelle en 2009

ContextAmong the adverse events in the blood transfusion process, transfusion to a “wrong” patient is potentially dangerous, as it can lead to an adverse reaction at least in case of ABO incompatible red cell concentrate.Material and methodsThe “Root Cause Analysis” working party of the National Hemovigilance Commission developed a tool to collect this type of adverse event, and tested it on a sample of 43 cases involving red cell concentrates notified between March, 2009 and February, 2010.ResultsOne hundred and nine failures of a step in the transfusion process were observed, i.e. 2.5 failures per adverse event. Failures may occur early in the process. However, they are mainly found at the time of issuing of the blood component, and further, in the clinical ward. How the failure is eventually detected is not always described when the blood component has been fully transfused, in contrast with the cases where actual transfusion to the wrong patient has been prevented. Knowing the way of failure detection enables an objective approach of the efficacy of the numerous existing safety measures. In this sample, bedside controls (documents check as well as the use of anti-A and anti-B reagents with patient's blood and red cell concentrates) detected the failure in three cases out of 34, which were not detected before, showing an efficacy similar to the administrative control done at reception in the clinical ward.ConclusionThe document, set up to analyse step by step these cases of patient errors, will be used in the future to analyse all similar cases, not only with red cell concentrates, but also with platelet concentrates and fresh frozen plasma, ultimately in order to improve their prevention.