Hypersensitivity reactions to blood components: document issued by the allergy committee of the French medicines and healthcare products regulatory agency.

These guidelines represent a consensus among experts on hypersensitivity reactions occurring after transfusion of blood components. They cover recognition, investigation, treatment, and prevention of such reactions. Implemented in France under the auspices of the French Medicines and Healthcare Products Regulatory Agency (AFSSAPS) and based on current knowledge, research, and experience, they aim to provide effective and easily teachable means of further improving the quality of hemovigilance databases, promote interest in this field, and help identify possible mechanisms and at-risk patient groups.

[Patient safety and root cause analysis]. / Sécurité des patients et analyse des causes racines.

Safety in the field of transfusion medicine has greatly improved in France. The risk of viral transmission has decreased by a factor greater than 1500 within the last 20 years. In comparison, the risk related to ABO error has decreased only by half. The reporting of critical incidents, which occur at any step of the transfusion procedure is now mandatory in France and is subject to an in-depth analysis, using methods close to that used in aviation safety. The goal of these analyses is to better understand human factors in order to implement more adequate prevention measures.

[Post-transfusion pulmonary oedema: the French hemovigilance network classification method]. / Œdèmes pulmonaires transfusionnels: classification des cas notifiés en hémovigilance.

Pulmonary oedema after transfusion of blood products may be hydrostatic (transfusion-associated circulatory overload [taco]) or exsudative (transfusion-related acute lung injury [trali]). Both conditions have been recognized as major hazards to transfusion recipients. Risk characterization is necessary to improve safety and to monitor trends in the national blood transfusion system. A collaborative multidisciplinary working group of the French National Hemovigilance Committee has proposed an analysis framework for case definitions and classification. The method relies on internationally used definitions and is adapted to the codification procedures used in the french transfusion incident reports electronic data management.

[The management of post donation information: a fundamental element of blood safety]. / La gestion des informations post-don: un élément fondamental de la sécurité transfusionnelle.

Post donation information management is a fundamental axis of haemovigilance in terms of blood safety. It requires an organization ensuring a permanent reactivity, a good sensitization of French National Blood Service professionals and needs also a strong awareness of blood donors. Previous identification of stakeholders to warn during these kinds of alerts is essential to avoid the use of any blood product presenting a potential risk. The recent implementation of a consensual internal document aims to target the reinforcement of a homogeneous decision-making process, combining blood product self-sufficiency and above all recipient safety.

[Pulmonary complications of transfusion (TACO-TRALI)]. / Complications pulmonaires de la transfusion (TACO-TRALI).

Pulmonary oedemas occurring during or after a blood transfusion appear as the most frequent serious immediate incidents in the French hemovigilance database. They include transfusion-associated circulatory overload (TACO) and transfusion-related acute lung injury (TRALI). TACO are a major cause of transfusion-related death in France. TRALI are more and more recognized and notified. In no case, pooled fresh frozen plasma (100 donations) treated with solvent-detergent were involved in French TRALI cases. A logigrame will allow hemovigilance officers to better classify pulmonary oedemas in e-fit, the French hemovigilance database.

[Introduction of platelet additive solution in platelet concentrates: towards a decrease of blood transfusion reactions]. / L'introduction de solutions de conservation dans les concentrés plaquettaires : vers une diminution des réactions transfusionnelles.

Platelet concentrates (PC) are used in thrombocytopenia for curative or preventive treatment for hemorrhagic risk. Since five years, additive solutions have been added in PCs for several reasons; one of them is to present an interest in the intolerance in plasma reactions. The literature data have shown that these solutions entail fewer allergic reactions than PCs kept in plasma. This study was reviewed on three years of transfusion in France. The main objective of this study was to see if there was a difference in frequency when these PCs were in solution or not. All adverse reactions in recipients (ARR) occurring among PCs recipients (with and without additive solution) were analysed. The categories of ARR specifically studied were: allergies, febril non haemolytic reactions (FNHR) and the category "unknown". This study shows that there is significantly lower incidence of allergies by introducing solution. For all ARRs, there is also a decrease in their frequency when PCs are in additive solution, it is significant except for the apheresis platelet concentrates. For categories FNHR and "unknown", the results are opposed and/or not significant. This study confirms that introduction of additive solutions in PCs is able to reduce some allergic transfusion reactions.

[Blood transfusion surveillance: organization and results]. / Hémovigilance: organisation et résultats.

Created by law in 1994, haemovigilance is a national system of surveillance and alarm, from blood collection to the follow up of the recipients, gathering and analysing all untoward effects of blood transfusion in order to correct their cause and prevent recurrence. Three levels compose the haemovigilance network: local, regional and national. The incident reporting is mandatory and this rate is stable with 2.9 to 3 incidents per 1000 blood components transfused. The transfusion incident due to bacterial contamination and ABO incompatibility worry the medical community. Haemovigilance contributes to transfusion safety. It makes possible to recognise risks already known, to be on alert for emergent risks, to undertake preventive actions on critical steps of the transfusion chain, and to warrant follow up of safety measures efficiency.

TCR alpha beta gene usage for myelin basic protein recognition in healthy monozygous twins.

The pathogenic role of myelin basic protein (MBP)-specific T lymphocytes in multiple sclerosis (MS) has been suggested by the encephalitogenicity of MBP-specific T cells in experimental allergic encephalomyelitis (EAE). In humans, extensive analysis of TCRs involved in MBP recognition has led to conflicting results, varying from an intra- and/or interindividual restriction to high diversity in TCRAV/TCRBV gene usage. We previously established MBP-specific T cell lines (TCLs) from healthy monozygous twins and characterized their fine epitope specificity. In this study, we report on the TCR alpha beta gene usage of 52 of these MBP TCLs that are specific for epitopes recognized by both co-twins within the same pair. High overall diversity in the TCR alpha and TCR beta genes used for recognition of this self-Ag, MBP, was observed. Variable genes belonging to 19 different TCRAV and 16 different TCRBV subfamilies are expressed by the 52 TCLs herein studied. In co-twins, TCLs utilized genes belonging to common TCRAV and/or TCRBV gene subfamilies in 7 of 13 instances of shared epitope recognition. Statistical analysis of intrapair concordance for TCR gene usage for the recognition of a given peptide did not show any significant deviation from values that would be anticipated in the absence of genetic background effect.

Healthy monozygous twins do not recognize identical T cell epitopes on the myelin basic protein autoantigen.

The T cell response against myelin basic protein (MBP) has been extensively studied in humans because of its putative role in the pathophysiology of multiple sclerosis (MS). Higher concordance rates in monozygous twins as well as an increased risk in relatives suggest the role of genetic factors in MS susceptibility. Very little is known about the shaping of T cell repertoire towards self antigens in humans and their contribution to disease susceptibility in autoimmune disorders. Here we report the comparative T cell epitope recognition patterns towards the MBP auto-antigen in healthy identical twins. We have established MBP-specific T cell lines from eight sets of twins and characterized their fine epitope specificity. Intra-pair comparison showed the co-existence of shared as well as distinct epitopes in six of eight pairs and a complete absence of concordant epitope recognition within two other pairs. These findings indicate that important differences in T cell repertoires against a self antigen may be observed between genetically identical healthy individuals, rendering difficult the interpretation of the differences which may be observed between identical twins discordant for an autoimmune disease.

Neocytopheresis: a new approach for the transfusion of patients with thalassaemia major.

At present the treatment of thalassaemia major consists of regular blood transfusions coupled with chelation therapy using deferoxamine. A complementary approach to the problem is the use of blood units enriched with young red cells (neocytes), which reduce the transfusional frequency and thereby diminish the risk of iron overload. Young red cell units were collected from blood from 60 volunteer donors using a cell separator (IBM 2997). Donors' blood was anticoagulated and the young red cell harvesting carried out over 4 h at a constant rotor speed of 500 rpm. Three biological criteria were used to evaluate young red cell quality: the number of reticulocytes, the pyruvate kinase activity and the mean corpuscular volume, all of which show an enrichment of young red cells as compared to standard donor units. The 51Cr young red cell survival in four normal donors and in two splenectomized patients showed an increased red cell half-life compared to the same study performed with standard blood units. Blood consumption was diminished significantly when the two patients were transfused with young red cell units. It must be emphasized that, despite the high cost of this blood product, the efficiency of this transfusion technique, by reducing blood consumption, represents important progress and a hopeful treatment for chronic anaemia.