Efficient and highly reproducible production of red blood cell-derived extracellular vesicle mimetics for the loading and delivery of RNA molecules

Extracellular vesicles (EVs) are promising natural nanocarriers for the delivery of therapeutic agents. As with any other kind of cell, red blood cells (RBCs) produce a limited number of EVs under physiological and pathological conditions. Thus, RBC-derived extracellular vesicles (RBCEVs) have been recently suggested as next-generation delivery systems for therapeutic purposes. In this paper, we show that thanks to their unique biological and physicochemical features, RBCs can be efficiently pre-loaded with several kinds of molecules and further used to generate RBCEVs. A physical vesiculation method, based on "soft extrusion", was developed, producing an extremely high yield of cargo-loaded RBCEV mimetics. The RBCEVs population has been deeply characterized according to the new guidelines MISEV2023, showing great homogeneity in terms of size, biological features, membrane architecture and cargo. In vitro preliminary results demonstrated that RBCEVs are abundantly internalized by cells and exert peculiar biological effects. Indeed, efficient loading and delivery of miR-210 by RBCEVs to HUVEC has been proven, as well as the inhibition of a known mRNA target. Of note, the bench-scale process can be scaled-up and translated into clinics. In conclusion, this investigation could open the way to a new biomimetic platform for RNA-based therapies and/or other therapeutic cargoes useful in several diseases.

Association between Blood Group and Change in Coagulation Factors in Plasma Preparations for Transfusion Purpose at Kisii Teaching and Referral Hospital

Background

Blood component therapy helps in managing patients with reduced hematopoiesis, elevated peripheral destruction of cells, and generalized blood loss (bleeding). Increased prevalence of arterial and venous thrombotic disease linked to the impact of ABO blood group on plasma levels of coagulation glycoprotein is demonstrated by blood group non-O persons.

Objective

This study had a main objective of determining the association between blood group and change in coagulation factors in plasma preparation for transfusion purpose.

Methods

The study employed a longitudinal study design. Factor assay evaluation was done by the use of Erba Mannheim ECL 105 semiautomated coagulation analyzer from India. Thawing meant for consequent coagulation factor analysis and sequential testing of stored cryoprecipitate and fresh frozen plasma was performed by the use of Stericox plasma thawing bath before being analyzed by the coagulation analyzer. Blood group of the collected blood sample in purple EDTA vacutainer was analyzed using blood antisera and a clean white tile, and results were recorded which helped in establishing the association existing between plasma and blood group. The data were fed into Excel and were evaluated by the use of SPSS version 25.

Results

There was no significant association between coagulation factors in fresh frozen plasma and blood group, coagulation factors in cryoprecipitate plasma and blood group of the donors showed that the relationship was not significant with, (r = -0.116, -0.097, 0.007 and 0.047 with p value (0.900, 0.087, 0.096 and 0.096), respectively, which are greater than 0.005 standard alpha value.

Conclusion

This study has shown no significant association existing between blood group and change in coagulation factors in plasma preparations at Kisii Teaching and Referral Hospital.

Comparison of Flow Cytometric Methods for the Enumeration of Residual Leucocytes in Leucoreduced Blood Products: A Multicenter Study

The BD FACSVia™ System features novel designs in hardware, software, and instrument QC. We compared the performance of the BD FACSVia System using the BD Leucocount™ kit with the BD FACSCalibur™ flow cytometer. Leucoreduced platelet (PLT, n = 252) and red blood cell (RBC, n = 278) specimens were enrolled at four sites. Each specimen was stained in four tubes using the BD Leucocount kit reagents and acquired on the two systems. BD Leucocount Control cells (high and low) were used to evaluate the inter-site reproducibility on the BD FACSVia System at three sites over 20 days. Deming regression and Bland-Altman analysis were performed to determine the WBC absolute counts on the BD FACSVia System vs. the BD FACSCalibur system. Assay accuracy for the range of 0-350 WBCs/µl was adequate. For samples with <25 WBCs/µl, the bias with 95% limits of agreement was 0.136 (-1.897 to 2.169) WBC/µl for PLTs (n = 184) and 0.170 (-2.025 to 2.365) WBC/µl for RBCs (n = 193). For inter-site reproducibility, the CV% was 6.46% (upper 95% CI 7.16%) for the PLT high control and 9.49% (10.52%) for the PLT low control. The CV% was 7.51% (8.32%) for the RBC high control and 10.76% (11.92%) for the RBC low control. The BD FACSVia System reported equivalent results of WBC absolute counts for leucoreduced PLT and RBC samples compared to the BD FACSCalibur system. The inter-laboratory reproducibility of the BD FACSVia System met study specifications. © 2018 The Authors. Cytometry Part A Published by Wiley Periodicals, Inc. on behalf of ISAC.

Ten-year follow-up of two cohorts with an increased risk of variant CJD: donors to individuals who later developed variant CJD and other recipients of these at-risk donors

BACKGROUND

Transmission of variant Creutzfeldt-Jakob disease (vCJD) through blood transfusion is implicated in three deaths and one asymptomatic infection. Based on this evidence, individuals assessed to be at increased risk of vCJD through donating blood transfused to individuals who later developed vCJD, or through being other recipients of such donors, are followed up to further understand the risks of vCJD transmission through blood.

OBJECTIVES

To provide a ten-year follow-up of these at-risk cohorts.

METHODS

Blood donors to patients who later died from vCJD were identified by the Transfusion Medicine Epidemiological Review (TMER) study. A reverse risk probability assessment quantified the risk of blood transfusion or exposure through diet as the source of vCJD in the recipients. Donors to these recipients, and these donors' other recipients, with a probability risk above 1%, are classified as at increased risk of vCJD for public health purposes. These cohorts are monitored for any vCJD occurrences.

RESULTS

A total of 112 donors and 33 other recipients of their donated blood have been classified as at increased risk. After 2397 and 492 vCJD-free years of follow-up, respectively, no deaths in either at-risk cohort were of vCJD-related causes.

CONCLUSIONS

The at-risk cohorts have survived disease-free far longer than the estimated incubation time for dietary-acquired vCJD (donors) and transfusion-acquired disease (other recipients). However, due to our still limited understanding of, and a lack of a reliable test for, asymptomatic vCJD infection, public health follow-up is necessary for continued monitoring of at-risk cohorts.

Evaluation of a red cell leukofilter performance and effect of buffy coat removal on filtration efficiency and post filtration storage

Prestorage leukoreduction of red cells is effective in reducing the incidence of HLA alloimmunization and improving the quality of stored packed red blood cells (PRBC). This study was conducted to evaluate the effectiveness of Imugard III-RC 4P in removing the leukocyte from packed red cells and the storage effects thereafter. The effects of buffy coat removal on the efficiency of leukofiltration, storage parameters of leukofiltered packed red blood cells and feasibility of prestorage leukofiltration were also assessed. Sixteen units each of buffy coat-depleted (LP) and nondepleted (NLP) PRBC were taken. Every unit was divided into two equal halves, one leukofiltered and other, non-leukofiltered. Cell counts, volume, hematocrit and hemoglobin were measured before and after filtration. Levels of K(+), lactate dehydrogenase (LDH) and hemolysis were assessed in all the units weekly, post leukofiltration. Post leukofiltration, red cell and volume loss was within the specified limit in all the units. Residual leukocytes were significantly lesser in LP- PRBC compared to NLPPRBC. K(+), LDH and hemolysis were significantly elevated in NLP- PRBC. Leukofiltered PRBC showed lesser elevation of K(+), LDH and hemolysis towards the end of the storage period as compared to their unfiltered counterparts. Leukofilter is capable of performing ~4 log reduction. Buffy coat removal prior to filtration improves the efficiency of leukofilter and aids in improving the storage of red cells in terms of hemolysis.

Leukoreduced blood components: Advantages and strategies for its implementation in developing countries

Removal of leucocytes from various blood products has been shown to minimize Febrile nonhemolytic transfusion reactions, HLA alloimmunization, platelet refractoriness in multitransfused patients and prevention of transmission of leukotropic viruses such as EBV and CMV. Rapidly growing size of hemato-oncological patients in our country requiring multiple transfusion of blood and components during the course of their management pose a great challenge to transfusion services to provide them red cell and platelet antigen matched products in alloimmunized subjects. Thus removal of leucocytes below a certain threshold, ≤ 5 × 10⁶ in a blood component certainly helps in prevention of alloimmunization and associated risks in these patients. Currently the best Leucoreduction can be achieved with the help of 3rd and 4th generation leukofilters, both in laboratory and patient bed side, and state of the art apheresis devices. The present article briefly reviews the current literature for pros and cons of leucofilteration and its scope of implementation in the cost constrained settings.

The effect of a leukodepletion model on the activation stage of platelets

The preparation of thrombocyte concentrates with filtration before storage (in-line) makes it possible to avoid the presence of mononuclear cells in the concentrate and proinflammatory cytokines. Therefore, this filtration may result with decreased activation of trombocyte receptors in vitro, which may improve therapeutic efficiancy. Methods. We compared two groups, each with 30 therapeutic doses of concentrated thrombocytes. We prepared the first group using the classic model from the buffy coat and the other with concentrated thrombocyte samples filtrated during sampling, so-called in-line, with the WBC filter Imuflex (Terumo). Mononuclear cells (MNC), thrombocyte, and erythrocyte counts in the units of concentrated thrombocytes were obtained on an automatic cell counter, and we used flow cytometry to measure the expression of surface thrombocyte receptors. The results demonstrated that the trombocytes prepared with pre-storage filtration contained a very low level of mononuclear cells and markedly reduced trombocyte receptors. Conclusion. The number of MNC and expression of surface thrombocyte receptors were markedly lower in the concentrated thrombocyte units prepared with in-line filtration. The thrombocytes prepared in this way contain fewer mononuclear cells, are of higher quality, are more functional, and may produce a better therapeutic effect in vivo.

Incidence and transfusion risk factors for transfusion-associated circulatory overload among medical intensive care unit patients

BACKGROUND

Transfusion-associated circulatory overload (TACO) is a frequent complication of blood transfusion. Investigations identifying risk factors for TACO in critically ill patients are lacking.

STUDY DESIGN AND METHODS

We performed a 2-year prospective cohort study of consecutive patients receiving blood product transfusion in the medical intensive care unit (ICU) of the tertiary care institution. Patients were followed for development of transfusion-related complications. TACO was defined as acute hydrostatic pulmonary edema occurring within 6 hours of transfusion. In a nested case-control design, transfusion characteristics were compared between cases (TACO) and controls after matching by age, sex, and ICU admission diagnostic category. In a secondary analysis, patient characteristics before transfusion were compared between cases (TACO) and randomly selected controls.

RESULTS

Fifty-one of 901 (6%) transfused patients developed TACO. Compared with matched controls, TACO cases had a more positive fluid balance (1.4 L vs. 0.8 L, p = 0.003), larger amount of plasma transfused (0.4 L vs. 0.07 L, p = 0.007), and faster rate of blood component transfusion (225 mL/hr vs. 168 mL/hr, p = 0.031). In a secondary analysis comparing TACO cases and random controls, left ventricular dysfunction before transfusion (odds ratio [OR], 8.23; 95% confidence interval [CI], 3.36-21.97) and plasma ordered for the reversal of anticoagulant (OR, 4.31; 95% CI, 1.45-14.30) were significantly related to the development of TACO.

CONCLUSION

Volume of transfused plasma and the rate of transfusion were identified as transfusion-specific risk factors for TACO. Left ventricular dysfunction and fresh-frozen plasma ordered for the reversal of anticoagulant were strong predictors of TACO before the onset of transfusion.

Leukocyte depletion for safe blood transfusion

Leukocytes have ability to distinguish between self cells (body own cells) and foreign (allogenic) cells on the basis of human leukocyte antigen (HLA) proteins that are present on the cell membrane and are effectively unique to a person. During allogenic blood transfusion a person receives large number of allogenic donor leukocytes and these are recognized as foreign cells by the recipient immune system which leads to several adverse reactions. To avoid such leukocyte-mediated adverse reactions leukodepleted blood transfusion is required. Leukocytes can be separated on the basis of size, dielectric properties, by affinity separation, freeze-thawing and centrifugation but all these methods are time consuming and costly. Filtration is another method for leukocyte depletion that is comparatively less expensive and more efficient as it gives more than 90% leukodepletion of blood along with minimal cell loss. However, present filtration procedures also have some limitations as they work efficiently with blood components but not with whole blood and show non-specific adhesion of large number of platelets and red blood cells along with leukocytes. All the currently available filters are costly, which has been a major reason for their limited application. Therefore, demand for a more efficient and cost-effective filter is high in medical community and scientists are attenpting to improve the efficiency of currently available filters. The present review gives an overview of the significance of leukodepleted blood transfusion and focuses on different methods for leukocyte depletion and challenges involved in all these technologies.

[Transfusion-related acute lung injury]

The term Transfusion-Related Acute Lung Injury (TRALI) was coined in 1985. It is a relatively rare, life-threatening clinical syndrome characterized by acute respiratory failure and non-cardiogenic pulmonary edema during or following a blood transfusion. Although its true incidence is unknown, a rate 1 out of every 5000 transfusions has been quoted. TRALI has been the most common cause of transfusion-related fatalities during three years in the USA. Two different etiologies have been proposed. The first is a single antibody-mediated event involving the transfusion of anti-HLA or antigranulocyte antibodies into patients whose leukocytes express the cognate antigens. The second is a two-event model: the first event is related to the clinical condition of the patient (sepsis, trauma, etc.) resulting in pulmonary endothelial activation and neutrophil sequestration, and the second event is the transfusion of a biologic response modifier that activates these adherent polymorphonuclear leukocytes resulting in endothelial damage and capillary leak. The patient management is support as needed based on the severity of the clinical picture and strategies to prevent TRALI are focused on: donor-exclusion policies, product management strategies and avoidance of unnecessary transfusions.

Clinical effects of different types of red cell concentrates in patients with thalassemia and sickle cell disease

The treatment of thalassemia is still essentially based on continuous transfusion supporting using red cell concentrates (RCC) prepared in different ways. For patients with sickle-cell disorders, either urgent or chronic red blood cell transfusion therapy, is widely used in the management of sickle cell disease (SCD) because it reduces HbS level and generally prevents recurrent vaso-occlusive disease (VOD). Recently, the introduction of pre-storage filtration to remove leukocytes and the use of techniques for multicomponent donation have increased the types of blood components available for transfusion purposes. The clinical effects of different types of blood components in thalassaemic and sickle-cell patients have not been extensively studied so far. We evaluated the impact of the various different blood components currently available on transfusion needs, transfusion intervals and adverse reactions in order to determine which is the most advantageous for transfusion-dependent thalassaemic and sickle-cell patients followed in our centre. We believe that the optimal characteristics of the RCC are aged less than 10 days from time of collection; Hb content greater than 56 g per unit; Hct: 55-60%; volume (including additive) 300 mL+/-20%; leucodepleted to less than 200,000 leukocytes per unit; low cytokine content (achievable by pre-storage filtration carried out between two and 24 hours after the collection); lack of microaggregates (achievable by pre-storage filtration or filtration in the laboratory) and protein content less than 0.5 g per unit for patients allergic to plasma proteins (achievable with manual or automated washing). It is still recommended that the blood transfused should be as fresh as possible, compatible with the centre's product availability and the centre's organisation should be continuously adapted to this aim. We always transfuse blood within 10 days of its collection, respecting Rh and Kell system phenotypes. Pre-storage filtration is strongly recommended, both in order to prevent adverse reactions through the marked leucodepletion (less than 200,000 leukocytes per unit) and for a better standardisation of the final product, including the certainty that the product does not contain clots, an assurance that bed-side filtration cannot give. The RCC should be produced using a method causing as little as possible stress to the red cell membrane. The use of RCC with a high content of Hb (less than 56 g per unit) is strongly recommended, because our study clearly shows that this reduces the number of exposures to donors and the number of accesses to hospital, thus improving the patient's quality of life.

The impact of universal leukodepletion of the blood supply on hemovigilance reports of posttransfusion purpura and transfusion-associated graft-versus-host disease

BACKGROUND

The pathogenesis of posttransfusion purpura (PTP) and transfusion-associated graft-versus-host disease (TA-GVHD) involves patient exposure to donor platelets (PLTs) and T lymphocytes, respectively, which are removed during blood component leukodepletion (LD).

STUDY DESIGN AND METHODS

Reports of PTP and TA-GVHD to the UK hemovigilance scheme Serious Hazards of Transfusion (SHOT) from 1996 to 2005 were compared before and after implementation of universal LD during 1999.

RESULTS

There were 45 reports of PTP, with a mean of 10.3 per year before universal LD and 2.3 per year afterward (p < 0.001). All patients had received red cells, but before universal LD, only 1 of 31 (3%) cases had also received PLTs, compared to 8 of 14 (57%) afterward (p < 0.001). Thirty-four cases (76%) had human platelet antigen (HPA)-1a antibodies, whereas 11 had antibodies to other HPA specificities, only 1 of which occurred after LD. Two cases reported before LD also had heparin-dependent PLT antibodies. There were 13 reports of TA-GVHD, all fatal, of which only 2 cases of undiagnosed immunodeficiency met current UK criteria for irradiated components. Eight others had one or more risk factors: B-cell malignancy (6), steroids (1), fresh blood (1), and donor-recipient HLA haplotype share (4). Eleven cases were due to non-LD and 2 to LD components (p < 0.001). No cases have been reported since 2001. In an additional 405 cases, nonirradiated components were transfused in error to high-risk recipients, mainly on fludarabine, but none developed TA-GVHD.

CONCLUSIONS

These findings suggest that universal LD has further reduced the already low risk of TA-GVHD in immunocompetent recipients and has altered the profile of PTP cases.

Creutzfeldt-Jakob disease and blood transfusion: results of the UK Transfusion Medicine Epidemiological Review study

BACKGROUND AND OBJECTIVES

This paper reports the results to 1 March 2006 of an ongoing UK study, the Transfusion Medicine Epidemiological Review (TMER), by the National CJD Surveillance Unit (NCJDSU) and the UK Blood Services (UKBS) to determine whether there is any evidence that Creutzfeldt-Jakob disease (CJD), including sporadic CJD (sCJD), familial CJD (fCJD), and variant CJD (vCJD) is transmissible via blood transfusion.

MATERIALS AND METHODS

Sporadic CJD and fCJD cases with a history of blood donation or transfusion are notified to UKBS. All vCJD cases aged > 17 years are notified to UKBS on diagnosis. A search for donation records is instigated and the fate of all donations is identified by lookback. For cases with a history of blood transfusion, hospital and UKBS records are searched to identify blood donors. Details of identified recipients and donors are checked against the NCJDSU register to establish if there are any matches.

RESULTS

CJD cases with donation history: 18/31 vCJD, 3/93 sCJD, and 3/5 fCJD cases reported as blood donors were confirmed to have donated labile components transfused to 66, 20, and 11 recipients respectively. Two vCJD recipients have appeared on the NCJDSU register as confirmed and probable vCJD cases. The latter developed symptoms of vCJD 6.5 years and 7.8 years respectively after receiving non-leucodepleted red blood cells (RBCs) from two different donors who developed clinical symptoms approximately 40 and 21 months after donating. A third recipient, given RBC donated by a further vCJD case approximately 18 months before onset of clinical symptoms, had abnormal prion protein in lymphoid tissue at post-mortem (5-years post-transfusion) but had no clinical symptoms of vCJD. CJD cases with history of transfusion: Hospital records for 7/11 vCJD and 7/52 sCJD cases included a history of transfusion of labile blood components donated by 125 and 24 donors respectively. Two recipients who developed vCJD were linked to donors who had already appeared on the NCJDSU register as vCJD cases (see above). No further links were established.

CONCLUSION

This study has identified three instances of probable transfusion transmission of vCJD infection, including two confirmed clinical cases and one pre- or sub-clinical infection. This study has not provided evidence, to date, of transmission of sCJD or fCJD by blood transfusion, but data on these forms of diseases are limited.

Outliers in RhD membrane integration are explained by variant RH haplotypes

BACKGROUND

Variations in a multipass transmembrane protein may affect its membrane integration. To study this effect, the systematic molecular characterization of variant D antigen density is a suitable model. Unlike most other membrane proteins, the expression of the D antigen is often determined by a single allele, because it occurs frequently in hemizygous form.

STUDY DESIGN AND METHODS

The D antigen density distribution of 530 CcDee, 475 ccDEe, and 514 ccDee random samples was established by flow cytometry. The molecular bases of samples with D antigen densities outside a bell-shaped peak was investigated.

RESULTS

The antigen densities of 499 CcDee, 437 ccDEe, and 480 ccDee samples formed bell-shaped peaks. Three, 10, and 12 samples, respectively, had decreased antigen densities and carried variant RHD alleles. Weak D type 19, RHD(I204T); weak D type 20, RHD(F417S); and the partial D DYU (also known as DQC), RHD(R234W) were new RHD alleles. Twenty-eight CcDee, 28 ccDEe, and 22 ccDee samples had increased antigen densities; 53 of them lacked a hybrid Rhesus box and were thus predicted to be RHD homozygous. Eight ccDee samples were predicted to be heterozygous despite a large relative dose of RHD to RHCE alleles in quantitative polymerase chain reaction. One of these samples was further investigated and carried an RHD-CE hybrid transcript characteristic for a -D- haplotype.

CONCLUSIONS

Unusual little and large RhD protein integration into the membrane could be traced to a host of distinct protein variants. Weak expression of D antigen was invariably associated with variant RHD alleles. Larger than normal D antigen density may often be caused by the presence of two D encoding alleles, which may be located in cis, and confounding zygosity testing that is solely based on gene copy number.

Transfusion independence in patients with myelodysplastic syndromes

Anemia is the most common cytopenia associated with myelodysplastic syndromes (MDS). Current management relies on frequent red blood cell (RBC) transfusions and erythroid growth factors to alleviate symptoms. However, the dependence of patients with MDS on repeated RBC transfusions often results in significant clinical and economic consequences, poorer outcomes, and diminished health-related quality of life. In addition, the intensity and duration of RBC transfusion dependence can influence responses to treatment after disease progression. Erythropoietic growth factors may alleviate the need for RBC transfusions in some patients with MDS, although only a minority of patients experience responses. Emerging treatment strategies to reduce or eliminate the need for RBC transfusions in patients with MDS include immunomodulating drugs, immunosuppressive therapy, and differentiating agents. The immunomodulating drug lenalidomide in patients who have MDS with 5q deletion is unique among emerging approaches, in that cytogenetic remitting activity and durable erythroid responses have been achieved. Newer treatments have the potential to improve the care of patients with MDS by alleviating the clinical, economic, and quality-of-life consequences of long-term RBC transfusion dependence.

Filter Buffy Coats (FBC): a source of peripheral blood leukocytes recovered from leukocyte depletion filters

In compliance with federal regulations, blood banks routinely use leukocyte depletion filters to eliminate contaminating leukocytes from blood products such as red blood cell and platelet concentrates. We developed and optimized conditions to elute leukocytes adsorbed to these filters; resulting in leukocyte suspensions which we termed Filter Buffy Coats (FBCs). These Filter Buffy Coats can replace standard buffy coats for various research applications. After optimizing both the filter elution medium as well as elution protocols, we compared commonly used leukocyte depletion filters from four different manufacturers. Relative fractions as well as total recoveries of leukocyte subsets, such as lymphocytes, monocytes and granulocytes, found in Filter Buffy Coats were identified and compared among the filters as well as to standard buffy coats and whole blood. Flow cytometric analysis of Filter Buffy Coats confirmed the presence of T- and B-lymphocytes, NK cells and monocytes. Furthermore, a significant quantity of CD34(+) hematopoietic stem or progenitor cells (HSC/HPC) was detected in Filter Buffy Coats prepared from different filters, thus making FBCs a valuable source for research on HSC/HPC. Colony assays revealed that most of these CD34(+) cells are functional. Using immunomagnetic cell sorting (MACS), we isolated a variety of leukocyte populations from FBC mononuclear cells (Filter-PBMCs) including T lymphocytes (CD4(+), CD8(+), CD3(+)), B lymphocytes (CD19(+)), NK cells (CD56(+)), HSC/HPC (CD34(+), CD133(+)) or dendritic cells (BDCA-4(+)). Functional properties of Filter-PBMCs, as well as of some of these isolated leukocyte populations, were confirmed using standard assays. In summary, Filter Buffy Coats are a valuable and convenient source of different peripheral leukocyte populations and can replace standard buffy coat preparations for research applications.

Pre-storage leucocyte depletion and transfusion reaction rates in cancer patients

Passenger leucocytes transfused with allogenic blood are responsible for potential adverse effects. The impact of pre-storage leucodepletion (in-line filtration) of all whole blood units on transfusion reaction rate among patients suffering from cancer was retrospectively studied, comparing all reactions following red blood cell (RBC) transfusions during 2 years of pre-storage vs. 2 years of selective (bedside) leucodepletion. During selective leucodepletion, 5165 RBC units - of which 2745 were bedside filtered units- were transfused to 866 patients. Twenty-eight reactions were recorded: 22 (15 in the bedside group) febrile non-haemolytic transfusion reactions (FNHTR) and six allergic reactions (five in the bedside group). The overall percentage of reactions was 0.54 (0.76 for bedside) and 0.42 for FNHTR (0.54 for bedside). During pre-storage leucodepletion, 4116 RBC units were transfused to 841 patients. Eleven reactions were recorded: four FNHTR and seven allergic reactions (urticaria). The percentage of reactions for transfused RBC units was 0.26 (0.09 for FNHTR). Comparison between pre-storage filtration and bedside filtration with regard to FNHTR showed an odds ratio of 2.80 (95% confidence interval = 0.83-14.87) for bedside filtration. The study suggests that, for transfused patients affected by cancer, pre-storage leucodepletion is more effective than selective (bedside) filtration in reducing the incidence of transfusion reactions (FNHTR).

Risks of blood transfusion

This article discusses advances in blood safety during the last 20 years, particularly for prevention of transfusion-transmitted viral infections. Although the most serious known risks from blood transfusion are administrative errors, transfusion-related acute lung injury, and bacterial contamination in platelet products, infection from emerging pathogens such as West Nile virus emphasizes the need for implementing proactive strategies. Pathogen inactivation technologies and reactive strategies such as nucleic acid testing ensure continued advances in blood safety.

The effect of universal leukoreduction on postoperative infections and length of hospital stay in elective orthopedic and cardiac surgery

BACKGROUND

A before and after study was undertaken to investigate the effect of universal leukoreduction (ULR) in the UK on postoperative length of hospital stay (LOS) and infections.

STUDY DESIGN AND METHODS

Consecutive patients undergoing elective coronary artery bypass grafting or total hip and/or knee replacement in 11 hospitals received non-WBC-reduced RBCs before implementation of ULR (T1, n=997) or WBC-reduced RBCs after implementation of ULR (T2, n=1098).

RESULTS

Patients in T1 and T2 were comparable except patients in T2 received on average more units of RBCs but had lower discharge Hct levels. Postoperative LOS (T1, 10 +/- 8.9 days; T2, 9.6 +/- 6.9 days) and the proportion of patients with suspected and proven postoperative infections (T1, 21.0%; T2, 20.0%) were unchanged before and after ULR (LOS, hazard ratio 1.01, 95% CI 0.92-1.10; infections, OR 0.83, 95% CI 0.77-1.02). Subgroup analysis showed no significant interaction between storage age or dose of blood on responsiveness of primary outcomes to ULR. Secondary outcomes were unchanged overall. Analysis by surgical procedure gave conflicting results with both increased mortality (p=0.031) and an increased proportion of cardiac patients with proven infections (p=0.004), whereas the proportion of orthopedic patients with proven infections was reduced (p=0.002) after ULR.

CONCLUSION

Implementation of ULR had no major impact on postoperative infection or LOS in patients undergoing elective surgical procedures who received transfusion(s). Smaller effects, either detrimental or beneficial of ULR, cannot be excluded.

Drug-induced myelosuppression : diagnosis and management

Myelosuppression is a common and anticipated adverse effect of cytotoxic chemotherapy. It is a potential but rare idiosyncratic effect with any other drug, but there is a recognised association with a number of higher-risk agents which justify additional vigilance. Genetic risk factors are being identified which may predispose individuals to this reaction with particular drugs. As marker tests become available, dose adjustment or alternative treatment choices may help to avoid more severe reactions. Myelosuppression is potentially life threatening because of the infection and bleeding complications of neutropenia and thrombocytopenia. Strategies for monitoring, early detection, diagnostic confirmation and appropriate supportive care are well developed for cytotoxic therapy. Developments in antimicrobial chemotherapy, blood product transfusion support and growth factor therapy have improved outcomes. These advances are largely applicable to idiosyncratic drug-induced myelosuppression, reinforcing the importance of early recognition and referral to appropriate expertise. Many reactions will resolve on drug withdrawal with appropriate supportive care during the period of cytopenia. Prolonged marrow failure may require more specific treatment with intensive immunosuppression or consideration of bone marrow transplantation.

Risks of blood transfusion

OBJECTIVE

To review the current status of risks of blood transfusion.

DATA SOURCES, EXTRACTIONS, AND SYNTHESIS

English-speaking literature, literature search using key works, human data, and follow-up with key bibliographic citations.

CONCLUSIONS

Substantial advances have been achieved in blood safety during the last 20 yrs, particularly for transfusion-transmitted viral infections. Currently, the most serious known risks from blood transfusion are administrative error (leading to ABO-incompatible blood transfusion), transfusion-related acute lung injury, and bacterial contamination in platelet products. Emerging pathogens, such as West Nile virus infection emphasize the need for implementation of proactive strategies, such as pathogen inactivation technologies, as well as reactive strategies, such as nucleic acid testing, to ensure continued advances in blood safety.

Filters in anaesthesia and intensive care

The use of various types of filters in anaesthesia and intensive care seems ubiquitous, yet authentication of the practice is scarce and controversies abound. This review examines evidence for the practice of using filters with blood and blood product transfusion (standard blood filter, microfilter, leucocyte depletion filter), infusion of fluids, breathing systems, epidural catheters, and at less common sites such as with Entonox inhalation in non-intubated patients, forced air convection warmers, and air-conditioning systems. For most filters, the literature failed to support routine usage, despite this seemingly being popular and innocuous. The controversies, as well as guidelines if available, for each type of filter, are discussed. The review aims to rationalize the place of various filters in the anaesthesia and intensive care environment.

Inline-filtration

BACKGROUND

Routine leukocyte-depletion (LD) of cellular blood products, and even plasma, is currently being implemented in most European countries, as a result of the fear that the variant Creutzfeldt-Jakob-disease (vCJD) might be transmissible by transfusion. However, not only is the scientific evidence supporting such a notion scarce, but the benefits of applying this procedure to all patients also remain unfounded.

METHODS

A MEDLINE-research for studies dealing with the indications for LD was performed. In addition, the guidelines and recommendations of national and international health authorities were scrutinized.

RESULTS

To date,the only proven benefit of LD that can be applied to all patients is the reduction of non-hemolytic febrile transfusion reactions. In addition, LD reduces HLA-immunization and platelet refractoriness in multi-transfused patients. In immunocompromized patients, LD reduces transfusion-transmitted CMV-disease. Furthermore, a minority of 5-10% of transfusion-related-acute-lung-injury cases can be prevented by LD. However, the potential of reducing the immunomodulating effects of transfusion such as postoperative infection, cancer-recurrence-related or overall mortality and of reducing septicemia due to bacterial contamination is still at issue. AIDS patients do not benefit from LD, at least. The suitability of LD for preventing the transmission of vCJD is at best hypothetical. Potential risks of LD like increased leakages have not been taken into account adequately to date.

CONCLUSIONS

At present, the scientific evidence does not justify the introduction of LD as a routine measure. In times of limited health care resources, this costly procedure might limit access to medical services with proven effectiveness and efficiency. In addition, the loss of 5-10% of the red cell pool is predicted to lead to more blood supply shortages than previously seen.

Value of central analysis of leucocyte depletion quality control data within the National Blood Service, England

BACKGROUND AND OBJECTIVES

The results of quality monitoring leucocyte counts were analysed nationally for the first 2 years of universal leucocyte depletion (LD), spanning the time-period before and after standardization of the counting and LD methods. The objectives were twofold: first to determine whether the implementation strategy was effective in achieving the LD specification (< 5 x 10(6) leucocytes in 99% of components with 95% statistical confidence); and second, whether quality monitoring was able to detect potential non-conformance.

MATERIALS AND METHODS

Residual leucocytes were counted using Beckman Coulter or Becton Dickinson (BD) flow cytometers and reagents. Data were collected into standardized analysis software (NWA Quality Analyst) for local trend analysis and checks for conformance to process specification, and collated centrally. Analysis was performed for six time-periods between January 1999 and March 2001. Specification failures were analysed to determine the likelihood of extreme failure. Statistical process monitoring was adjusted to suit LD processes.

RESULTS

Data from red cells in optimal additive solution (OAS), filtered either as whole blood or red cell concentrates, and platelet pools improved significantly over the 2-year period with specification failures falling from 0.35%, 0.48% and 0.56%, respectively, in January-June 1999 to 0.06%, 0.01% and 0.04% in January-March 2001. Specification failures in red cells in OAS LD for the period January-December 2000 showed only 0.02% with a leucocyte count of > 30 x 10(6)/unit. Extreme failures are now very rare. Monitoring methods have been effective in detecting process change and drift.

CONCLUSION

LD performance varies between different LD systems, but monitoring has proved sufficiently robust to detect processes that perform poorly. The chosen specification has been both achievable and appropriate to the systems in use. Standardization of the counting method is central to the ability to monitor and analyse results effectively across the whole service.

The development of a national standardized approach for the enumeration of residual leucocytes in blood components

BACKGROUND AND OBJECTIVES

The UK Blood Transfusion Services implemented universal leucocyte depletion of the blood supply in November 1999. To provide statistical process monitoring of these processes, automated methods were introduced to count residual leucocytes (white blood cells) in blood components.

MATERIALS AND METHODS

Initially in the National Blood Service (NBS) England, protocols were standardized on the use of LeucoCount reagents with either Becton-Dickinson or Beckman Coulter flow cytometers.

RESULTS

Standardization of protocols resulted in a decreased intersite variability of red cell samples (from 36% to 9% at a level of 11 and 10 cells/ micro l, respectively), and 100% of sites (n = 11) fulfilled the validation criteria. However, we also evaluated the use of alternative reagents with the result that reagents from either Becton-Dickinson or Beckman Coulter, used on either a Becton-Dickinson or Beckman Coulter flow cytometer, passed our validation criteria.

CONCLUSIONS

It is critical to include samples from filtered products containing white blood cells in validations of leucocyte enumeration methodology, as results may differ between methods using these samples but not using spiked or fixed material. Standardized gating strategies and optimization methods for flow cytometers are critical for obtaining equivalent results with different reagents and instruments.

Limited efficacy of universal leucodepletion in reducing the incidence of febrile nonhaemolytic reactions in red cell transfusions

This article demonstrates a 62% reduction in the number of febrile nonhaemolytic transfusion reactions (FNHTRs) and 50% reduction in febrile reaction rate associated with red cell transfusions following graded introduction of universal leucodepletion. Though this is a statistically significant reduction (P = 0.009), it shows limited efficacy in abrogating this complication. We also found a reduction in the proportion of cases of FNHTRs with lymphocytotoxic antibodies over the period studied from 54% in 1998, 28% in 1999 to 23% in 2000. This corresponds to a relative increase in the number of febrile reactions without human leucocyte antigen (HLA) antibodies following full implementation of universal leucodepletion, as the total number of reported reactions actually fell considerably during the period. The increase in the number of cases without HLA antibodies was directly proportional to the increase in the number of leucodepleted units used.

The United Kingdom National External Quality Assessment Scheme gating and standardization strategy for use in residual WBC counting of WBC-reduced blood components

BACKGROUND

Major causes of interlaboratory variation in low-level WBC counting are the gating strategies and staining methods employed. To overcome these limitations, a stable low-level WBC control preparation (termed daily run control [DRC]) was developed that when coupled with a new gating strategy will enable international standardization.

STUDY DESIGN AND METHODS

Both a whole blood preparation (stability of more than 12 months; target WBC count of 20 cells/microL with defined fluorescence values) and a new gating strategy were developed and used with a staining kit (LeucoCOUNT [Becton Dickinson BioSciences] providing the basis for standardization). These were then combined and used to crosscalibrate seven different flow cytometers. After standardization with the DRC, comparative studies were undertaken with fresh samples with a WBC range of <1 to 60 cells per microL.

RESULTS

The developed gating strategy enabled the DRC WBCs to be positioned to within four channels of the expected target fluorescence 1 value (2.3% variation) and within three channels of the target fluorescence 2 value (0.7% variation) on all evaluated instruments. Subsequent analysis of any sample meant that the WBCs always occupied the same "sample space," irrespective of flow cytometer platform and without the need for repositioning of the analysis region and/or gate.

CONCLUSION

The cross calibration and standardization of flow cytometers used for low-level WBC counting (irrespective of platform) are attainable with this United Kingdom National External Quality Assessment Scheme strategy. Its adoption should reduce interlaboratory CVs and provide a practical approach for the rapid identification of operator and machine problems.

Characterization and functional analysis of granulocyte concentrates collected from donors after repeated G-CSF stimulation

BACKGROUND

Neutropenic patients often develop bacterial or fungal infections not responding to broad-spectrum antibacterial or antifungal agents. Clinical efforts were made with transfusion of granulocyte concentrates; however, functions of granulocytes after multiple G-CSF stimulations and after apheresis are not yet investigated and described sufficiently.

STUDY DESIGN AND METHODS

The aim of this study was to characterize functional and immunologic variables of granulocytes in blood samples drawn from donors before and after each stimulation episode with G-CSF, in the resulting granulocyte concentrates and in the patients 8 hours after transfusion.

RESULTS

Chemotaxis was not influenced, neither by G-CSF application nor by apheresis. Multiple G-CSF stimulations enhanced oxidative burst and phagocytosis of Escherichia coli in donor granulocytes. These values returned to basal levels in granulocyte concentrates. Expression of granulocytic surface antigens was downregulated after application of G-CSF but returned to normal and in part enhanced values in concentrates. A clinically relevant increase of proinflammatory cytokines could not be detected. Leukotriene B4 production was reduced after the fourth G-CSF stimulation in the donor blood and enhanced in the granulocyte concentrate after apheresis. Results in recipients indicate that changes of granulocyte function noted in concentrates were only transient.

CONCLUSION

Stimulation of healthy donors with repeated G-CSF injections and subsequent granulocyte apheresis does not dramatically change decisive functions of granulocytes.

Clinical management of beta-thalassemia major

Management of patients with beta-thalassemia is based on adequate, safe blood transfusions (free of transfusion-transmitted diseases) and prevention of iron overload. Iron overload causes multiple endocrinopathies, contributes to osteoporosis, and is the cause of cardiac disease. Cardiac disease, secondary to iron damage, causes death in developed countries as a result of noncompliance to deferoxamine from the third decade of life. In underdeveloped countries, cardiac death starts from 12 years of age, due to nonavailability of deferoxamine. With the emergence of the advanced cardiac magnetic resonance imaging technique, early diagnosis of heart iron will allow the currently available iron-chelating agents (oral and parenteral) to be used in an innovative way to improve the quality of life and improve survival of patients with beta-thalassemia.

Revisitation of the clinical indications for the transfusion of platelet concentrates

Platelet transfusion is indicated when the expected benefits of increasing the number of functional platelets in the patient's circulation outweigh the potential risks generated by exposing the patient to allogeneic, manipulated and stored blood products such as platelet concentrates. Although reassuring evidence has been collected indicating that current risks associated with blood transfusion are lower than those of several voluntary and involuntary human activities, balancing benefits and risks of platelet transfusion may not be easy in a proportion of patients and in a number of conditions. To facilitate this task, guidelines have been developed, with particular attention to cancer patients. As witnessed by the most recent guidelines, over the last few years there has been a progressive, although not absolute, consensus on: (i) the routine use of platelets as a tool to prevent hemorrhage in oncohematology (the so called 'prophylactic approach') as opposed to limiting platelet transfusion to actual bleeding episodes (the so-called 'therapeutic approach') and (ii) lowering the trigger for prophylactic platelet transfusion in stable oncohematology recipients from 20 x 109 to 10 x 109 platelets/L. This has been accompanied by a reduction of platelet use per oncohematology patient of about 20%, an important outcome in view of the progressive increase of platelet demand due to more aggressive therapy in cancer patients. In selected clinical conditions, specific triggers ranging from 30 x 10(9) to 100 x 10(9) platelets/L have been recommended, with higher values when surgical procedures are required for the patient's treatment. Indications and trigger values proposed in the guidelines must be considered within the context of careful clinical evaluation of each patient, with a clear appreciation of the power of discrimination of automated platelet counters at low counts, and of the quality and local availability of platelet products for emergency.

WBC reduction in RBC concentrates by prestorage filtration: multicenter experience

BACKGROUND

As universal leukocyte (WBC) reduction (ULR) is being considered as a new standard, few data are available on the performance of WBC-reduction filtration in routine practice. The performance of WBC-reduction in RBCs, using varied filtration practices, in meeting the current FDA requirement (<5 x 10(6)), Council of Europe (EC) recommendation, the proposed FDA requirement (<1 x 10(6)), and a more stringent proposal (<5 x 10(5)) for residual WBCs per RBC unit was assessed and compared.

STUDY DESIGN AND METHODS

Participating facilities were the 11 sites of the Viral Activation Transfusion Study (VATS), a prospective study of the impact of transfusion with and without WBC-reduction on survival and HIV viral load in HIV-1-infected patients. Patients randomly assigned to undergo WBC reduction were required to receive RBCs < or =14 days old that had undergone prestorage (within 72 hours of collection) WBC-reduction filtration by a method devised to achieve a postfiltration WBC count of <5 x 10(6). Residual WBC quantitation was performed by PCR in the central VATS laboratory by using frozen WBC-reduced RBC samples obtained at issue for transfusion.

RESULTS

A total of 1869 WBC-reduced RBC units were studied. Filtration practices varied within and between sites. There were significant differences in mean residual WBC counts at the 11 sites (p<0.001). Among the WBC-reduced RBC units, 0.8 percent exceeded 5 x 10(6) WBCs per unit, 8.3 percent exceeded 1 x 10(6) WBCs per unit, and 14.3 percent exceeded 5 x 10(5) WBCs per unit.

CONCLUSION

Residual WBCs in WBC-reduced RBC units vary within and between sites. WBC reduction was successful, in that over 99 percent and 91 percent of VATS WBC-reduced RBC units met US and EC thresholds, respectively. However, the small but measurable failure rate indicates that not every unit will meet these guidelines.

The effect of leucocyte depletion on the quality of fresh-frozen plasma

The aim of this study was to evaluate the quality of leucodepleted (LD) fresh-frozen plasma (FFP) produced using one of five whole blood filters (Baxter RS2000 & RZ2000, NPBI T2926, Macopharma LST1 and Terumo WBSP) or two plasma filters (Pall LPS1 and Baxter FGR7014). Whole blood or plasma was filtered within 8 h of collection at an ambient temperature. Samples were taken pre- and post filtration for analysis of coagulation factors and complement activation (n = 7--12 for each type of filter). All filtered units (209--286 ml) contained < 5 x 10(6) residual leucocytes and < 30 x 10(9)/l platelets. Statistically significant losses of factors V, VIII, IX, XI and XII and increases in markers of coagulation activation were observed (0--21%), which were dependent on filter type. None of the filters had a significant effect on von Willebrand factor (VWF) multimeric distribution or the activity of VWF and factors II, VII or X. The effect on levels of C3a appeared to be related to the filter surface charge: positively charged filters resulted in C3a generation, whereas negatively charged resulted in C3a removal. None of the observed changes are likely to be clinically significant unless subsequent processing of plasma (such as pathogen inactivation) results in further losses of coagulation factors.

Paediatric transfusion

Paediatric transfusion encompasses a wide range of clinical circumstances including the consideration of maternal antibodies, the changing nature of the transfusion recipient with respect to growth and development, and the management of inherited conditions which if optimally treated in early life may have problems which are delayed or less severe in adult life. Whilst the transfusion of adults and children has much in common, a child cannot be considered as a scaled down adult; there are many important differences. Developmental changes are most marked in the neonate and, together with the fact that their antibodies are maternally derived, this population provide some of the most striking challenges. The increased use of intra uterine transfusion adds an extra dimension here. A particular paediatric concern is the long-term consequences of transfusion. It is to be hoped that paediatric transfusion recipients will live long enough that any potential problems will manifest themselves, thus the aim must be to minimize transfusion risks.

High frequency of positive surveillance for cytomegalovirus (CMV) by PCR in allograft recipients at low risk of CMV

Cytomegalovirus (CMV) causes significant morbidity and mortality following allogeneic haemopoietic stem cell transplantation. A pre-emptive strategy for ganciclovir therapy is widely used, where treatment is commenced on finding positive evidence of CMV replication. Surveillance by PCR has increased the sensitivity for CMV detection, but it is not known whether this may detect cases with evidence of CMV DNAemia who have a low probability of CMV disease. We reviewed our experience of CMV infection and disease since introducing CMV surveillance by PCR. All 30 allografts received bedside leucodepleted CMV-negative blood products. Seven of 10 CMV-positive recipients of a CMV-positive graft developed CMV DNAemia, with three developing clinical disease requiring ganciclovir treatment. In contrast, of 11 low risk patients (CMV-negative recipients of CMV-negative grafts), six developed evidence of CMV DNAemia although only one had clinical evidence of CMV disease requiring ganciclovir. Transfusion records confirmed that four of these had received exclusively CMV-negative blood products. The aetiology of the CMV DNAemia in these cases is unclear. It is suggested that before commencing ganciclovir therapy, confirmatory CMV antigenaemia testing is carried out on samples which test positive for CMV DNA, unless there is high clinical suspicion of CMV disease.

Low level leucocyte counting: a critical variable in the validation of leucodepleted blood transfusion components as highlighted by an external quality assessment study

Leucocyte counts of < 5 x 106 per blood transfusion product are currently recommended in the UK in order to reduce transfusion-related infections and febrile reactions. Routine leucocyte depletion, however, requires the development of reliable internal and external quality assurance (EQA) programmes. We report preliminary findings from the UK NEQAS for Low-Level Leucocyte Counting from 18 UK Transfusion Centres over a four month period. Data analysis showed that the IMAGN 2000 had the lowest CVs (range 7.5-36%, mean 16.7) for samples with counts of 5-30 cells/microl when compared to the flow cytometric (range 13.8-88%, mean 29.5) and Nageotte methods (range 20.6-117%, mean 61.8). In addition, laboratories using commercial nuclear stains (LeucoCOUNTTM) had consistently lower CVs than those using 'in-house' propidium iodide staining methods. Important differences in flow cytometric gating strategies were also identified. This study highlights the current variability in low level leucocyte counting, especially within the critical range of 5-30 cells/microl (equating to < 5 x 106/l). The acceptance of consensus protocols, including gating strategies and nuclear staining techniques, is required to reduce the observed interlaboratory variation. Finally, we demonstrate that stabilized blood preparations can be successfully used to provide a national/international low-level leucocyte EQA scheme.

Statistical process monitoring of WBC-reduced blood components assessed by two types of software

BACKGROUND

Statistical process control is required for monitoring of the WBC-reduction process. This study focused on some factors that may influence the outcomes of statistical process monitoring, such as WBC-reduction technologies, the anticoagulant used, and WBC-counting technologies, by using two types of software.

STUDY DESIGN AND METHODS

Data were collected from January to September 1999, before the implementation of universal WBC reduction. The effects of three major factors were investigated: methods of preparation, the addition of EDTA to the sample, and the WBC-counting technologies used (microvolume fluorimetry, flow cytometry, and Nageotte chamber). The WBC-reduction process capability was assessed by two types of software, EZQC (Gambro BCT) and NWA (Northwest Analytical). In addition, the differences between various sets of results were compared by the t test or ANOVA.

RESULTS

There was no statistical difference (at the 0.05 level of significance) in WBC content when the three types of platelets in citrate samples were compared with EDTA samples. In general, the Nageotte chamber appeared to count the lowest, and microvolume fluorimetry appeared to count lower than flow cytometry. There were minor but significant methodologic differences between the software packages. However, these differences had negligible effects on the percentage of conforming components at both <1 x 10(6) and <5 x 10(6) WBCs per unit.

CONCLUSION

Only the counting technologies were sufficiently different to warrant consideration. This difference may make unacceptable the interchange of results obtained from various counting methods.

Relative cost of autologous red cell salvage versus allogeneic red cell transfusion during abdominal aortic aneurysm repair

The costs of washed autologous red cell concentrate obtained by intraoperative red cell salvage were compared to the costs of allogeneic packed red cell transfusion during 110 consecutive abdominal aortic aneurysm repairs. The mean volume of scavenged blood during elective procedures was 1350 ml (range 350 to 6675 ml, n = 90) and emergency procedures 2750 ml (range 750 to 9400 ml, n = 20). The mean volume of processed (washed) blood returned during elective repairs was 759 ml (range 150 to 2900 ml, n = 51) and emergency repairs 1117 ml (range 0 to 4100 ml, n = 20). During elective repairs, the cost of routine autologous red cell salvage ($151 per 285 ml unit) was only slightly greater than the estimated cost of cross-matched, leucocyte-reduced, allogeneic blood ($143 per 285 ml unit). During emergency repairs, washed autologous red cells ($83 per 285 ml unit) were less expensive than allogeneic packed red cells. These findings indicate that, compared with the use of allogeneic packed red cells, red cell salvage during emergency abdominal aortic aneurysm repair can be justified on an economic basis alone, and that routine red cell salvage during elective repair can achieve the benefits of autologous blood at little extra cost to the community.

The management of alloimmune neonatal thrombocytopenia

Neonatal alloimmune thrombocytopenia (NAITP), defined as thrombocytopenia (platelet count < 150 x 10(9)/l) due to transplacentally acquired maternal platelet alloantibodies, occurs in approximately 1 per 1200 live births in a Caucasian population. In such a population, the majority (> 75 percent) of cases are due to fetomaternal incompatibility for the platelet specific alloantigen, HPA-1a (P1A1, Zwa). Incompatibility for the HPA-5b (Bra) alloantigen is the next most frequent cause of NAITP in Caucasians; much less common is NAITP due to incompatibility for HLA, blood group ABO or other platelet-specific antigens. In non-Caucasian populations (e.g. Orientals) HPA-1a incompatibility is a rare cause of NAITP and other alloantigens e.g. HPA-4b (Penb, Yuka) are implicated. The greatest clinical challenge relates to the antenatal management of pregnant women alloimmunized to the HPA-1a (P1A1, Zwa) antigen, and particularly the subset of such women who have a history of a previously affected infant with severe thrombocytopenia and/or intracranial hemorrhage (ICH). The risk of antenatal ICH in the fetus of such women is high enough to merit intervention, either weekly infusion of high-dose intravenous immunoglobulin G (IVIG) with or without corticosteroids given to the mother (the preferred approach in North American centres), or repeated in-utero fetal platelet transfusions (the preferred treatment approach in some European centres). Post-natal management of severely affected infants centres on the rapid provision of compatible antigen-negative platelets harvested from the mother or a phenotyped donor. The value of antenatal screening programs to detect 'at risk' alloimmunized women during pregnancy continues to be debated.

Leucocyte depletion of blood components

Universal leucocyte depletion has been implemented in the UK and several other European countries as a precautionary measure against the potential risk of transmission of variant Creutzfeldt-Jakob disease by blood transfusion. Leucocyte depletion had previously only been recommended for a relatively small proportion of transfusion recipients based on clinical and experimental evidence showing clinical benefit. However there is now increasing evidence to support its value in preventing transfusion transmission of infectious agents and in reducing some of the adverse immunomodulatory effects of allogeneic transfusion. The financial costs of providing universal leucocyte depletion are substantial, but, if it transpires that leucocyte depletion has a beneficial effect in reducing, for example, postoperative infection rates, then the health economic gains in this patient group alone may largely or wholly offset these financial costs. The experience in the UK and other European countries in terms of these collateral clinical benefits will help other countries, where the risk of variant Creutzfeldt-Jakob disease may not be so great, to decide whether to similarly adopt universal leucocyte depletion.