Clinical and laboratory precautions that reduce the adverse reactions, alloimmunization, infectivity, and possibly immunomodulation associated with homologous transfusions

Quality Assessment of Established and Emerging Blood Components for Transfusion

Blood is donated either as whole blood, with subsequent component processing, or through the use of apheresis devices that extract one or more components and return the rest of the donation to the donor. Blood component therapy supplanted whole blood transfusion in industrialized countries in the middle of the twentieth century and remains the standard of care for the majority of patients receiving a transfusion. Traditionally, blood has been processed into three main blood products: red blood cell concentrates; platelet concentrates; and transfusable plasma. Ensuring that these products are of high quality and that they deliver their intended benefits to patients throughout their shelf-life is a complex task. Further complexity has been added with the development of products stored under nonstandard conditions or subjected to additional manufacturing steps (e.g., cryopreserved platelets, irradiated red cells, and lyophilized plasma). Here we review established and emerging methodologies for assessing blood product quality and address controversies and uncertainties in this thriving and active field of investigation.

Comparative Study of Predeposit and Bedside Leucodepletion Filters

BACKGROUND

Removal of leucocytes from cellular blood components is associated with reduction of several transfusion associated adverse reactions.

METHODS

A total of 400 units of packed red blood cells (RBCs) were subjected to leucodepletion at room temperature and 4°C using different commercially available prestorage and bedside filters (Terumo Penpol Immugard III and Pall Medical BPF-4). Pre-filtration and post-filtration parameters were compared to assess the efficacy of prestorage leucodepletion vis-à-vis bedside leucodepletion and the requirement of universal leucodepletion.

RESULT

Mean post-filtration red cell recovery ranged from 88.49-93.49% with all bags showing more than 85% red cell recovery. Mean post-filtration residual leucocyte count ranged from 0.205 × 10(6)-0.338 × 10(6)/bag with all bags showing more than log 3 leucoreduction. Prestorage leucoreduction achieved by the polyurethane filter was better than that achieved by the polyester filter. Red cell recovery with the bedside filters at room temperature was significantly less than that with prestorage filters at either temperature.

CONCLUSION

This study suggests that prestorage leucoreduction is preferable over bedside leucoreduction and that polyurethane filters are better than polyester filters since leucodepletion achieved with the former is higher. We recommend selective log 3 leucodepletion using polyurethane prestorage filters for patients with specific indications.

Evaluation of performance of white blood cell reduction filters: an original flow cytometric method for detection and quantification of cell-derived membrane fragments

BACKGROUND

Contamination of blood products by white blood cells leads to a risk of transmission of infectious agents, particularly abnormal prion protein, the probable causative agent of new-variant Creutzfeldt-Jakob disease. Blood product filtration could reduce this risk, but the filtration systems might generate potentially infectious membrane fragments. We developed an original flow cytometric method that allows the detection and quantification of membrane fragments in filtered products and the evaluation of the quantity of destroyed cells.

METHODS

This method has four technical requirements: cytofluorometric acquisition of forward scatter parameters on a log scale, use of a fluorescent aliphatic reporter molecule (PKH26-GL) to identify membrane fragments, quantification with fluorescent beads, and the drawing up of a standard curve on the basis of cells destroyed by freezing/thawing to generate cell debris (i.e., quantity of membrane fragments measured versus quantity of destroyed cells).

RESULTS AND CONCLUSIONS

This original method can be used to test new filtration devices and it allows optimization of the filtration process or comparison of different filtration systems. We tested the method with three commercial white cell removal filters. We demonstrated that it is possible to evaluate the filter quality, particularly the likelihood of fragment removal during the filtration process.

Synthesis and characterisation of phosphorylcholine-based polymers useful for coating blood filtration devices

Copolymers of 2-methacryloyloxyethylphosphorylcholine (MPC) and lauryl methacrylate (LMA) of molar ratios MPC: LMAX where x = 1, 2 or 4, have been synthesised by two different free-radical polymerisation techniques. The solubility characteristics of the resulting materials were investigated in a variety of water: alcohol solvent mixtures and found to be influenced not only by the molar ratio of MPC: LMA, but also the method of synthesis. A window of solubility was observed for certain copolymers and the alcohol used in the solvent mixture was also found to have a profound influence on the solubility profile of the polymers. These materials were soluble in a wider range of aqueous methanol mixtures compared to aqueous mixtures of higher aliphatic alcohols, such as ethanol or isopropyl alcohol, which was rationalised in terms of the affinity of the phosphorylcholine headgroup for the various alcohols relative to water. 1H nuclear magnetic resonance spectroscopy was used to further examine the solution properties of the copolymers in various solvents. The copolymer MPC: LMA2 was coated onto a variety of substrates from both alcohol-only and water: alcohol solvent systems and the surface properties of the films compared by static and dynamic contact angle, atomic force microscopy (AFM) and attenuated internal reflectance Fourier transform infrared spectroscopy (ATR-IR). The coating formed from the water: alcohol solvent was found to be hydrophilic in nature, possessing spontaneous wettability, whereas films formed from alcohol-only solvents were hydrophobic, and only on conditioning with water were more wettable surfaces attained. This phenomenon was applied in the coating of leukocyte filtration material, where the aqueous-based systems demonstrated lower critical wetting surface tension (CWST) and shorter wetting times relative to both uncoated filters and those coated from alcohol-only systems. The haemocompatibility of the coated filters was equivalent for both coating solvent systems. employed, and far superior when compared to the uncoated control.

Filtration of RBC units:effect of storage time and temperature on filter performance

BACKGROUND

The influence of time, temperature, and rate of filtration on the efficacy of WBC reduction of RBC units was studied in a controlled, paired-donor format.

STUDY DESIGN AND METHODS

Ten donors underwent whole-blood phlebotomy on two to four occasions each. Units were filtered (RCXL-1, Pall Biomedical) under laboratory conditions and gravity flow as follows: 1) after 0 to 2 hours of storage at 22 degrees C, 2) after 7 to 8 hours at 22 degrees C, 3) after 14 days of storage at 4 degrees C, and 4) under mock bedside conditions after 14 days of storage at 4 degrees C. Prefiltration and postfiltration cell counts and prefiltration WBC CD11a expression were assessed on Days 0 and 14.

RESULTS

WBC content before filtration was 2.20 and 2.34 x 10(9) (p>0.05) for units stored for 2 and 8 hours (Groups 1 and 2) and declined to 52.8 and 7. 57 x 10(4) (p<0.01) after filtration. The efficacy of WBC reduction in units stored for 14 days was similar to that in units stored for 8 hours, but absolute postfiltration WBC counts were significantly lower because of a 0.6 log reduction in the starting WBC count after 14 days of storage (postfiltration WBC content of 1.02 and 2.31 x 10(4) for units filtered under laboratory vs. bedside conditions [p>0.05]). Filtration under bedside conditions was associated with a greater degree of variation in residual WBC counts than laboratory filtration. WBC reduction by filtration was significantly greater in units stored for at least 8 hours (Groups 2, 3, and 4) than in those stored for less than 2 hours (4.59 log vs. 3.83 log reduction in WBC content, p<0.05). Surface expression of leukocyte function antigen 1 as measured by CD11a was similar in all groups.

CONCLUSION

WBC reduction of RBC units by filtration was least effective when performed within 2 hours of collection. Efficacy of WBC reduction increased significantly after the units were stored for 8 hours to 14 days, without significant differences between these storage intervals. Laboratory filtration yielded more consistent results than did mock bedside filtration. Temperature and filtration rate had no effect on the efficacy of WBC reduction by filtration.

Leucodepletion of blood products by filtration

The leucocytes present in red cell and platelet components have been implicated in several important immunological and infective complications of blood transfusion. Recent developments in blood filtration technology allow the production of leucodepleted blood products (residual leucocytes < 5 x 10(6) per transfused unit) in the laboratory or at the bedside with the potential to prevent these adverse effects. Quality assurance remains an important problem, particularly for bedside filtration. Prestorage filtration may have significant advantages for red cell and platelet production. There is strong clinical evidence that 3 log10 leucodepletion prevents or delays febrile reactions in patients receiving multiple red cell transfusions and can reduce cytomegalovirus transmission. Leucodepletion to prevent HLA alloimmunisation, platelet refractoriness and febrile reactions in patients receiving red cell and platelet support remains controversial. Transfused leucocytes induce 'immunosuppressive' changes in the recipient, but recent studies cast doubt on the association with cancer recurrence after surgery. However, leucodepleted blood may reduce the incidence of postoperative infection. Leucodepletion by filtration is expensive and there is a requirement for well-designed prospective clinical studies focusing on appropriate filtration technology (and alternatives), clinical outcome and cost-effectiveness.

A mathematical model for the leukocyte filtration process

Leukocyte filters are applied clinically to remove leukocytes from blood. In order to optimize leukocyte filters, a mathematical model to describe the leukocyte filtration process was developed by modification of a general theoretical model for depth filtration. The model presented here can be used to predict the time-dependent leukocyte filtration as a function of cell-cell interaction in the filter, filter efficiency, filter capacity, filter dimensions, and leukocyte concentration in the suspension applied to the filter. The results of different leukocyte filtration experiments previously reported in the literature could be well described by the present model. (c) 1995 John Wiley & Sons, Inc.

Poly(ethyleneimine) modified filters for the removal of leukocytes from blood

Polyurethane membrane filters and filters coated with poly(ethyleneimine) were used to investigate the influence of leukocyte adhesion during filtration. Treatment of the filters with an aqueous solution of 1% (w/v) poly(ethyleneimine) (PEI) led to the introduction of amine groups at the filter surfaces, as was confirmed by X-ray photoelectron spectroscopy. The modification procedure did not significantly change the porous structure in the filters, as was demonstrated by SEM and porometry. Using 14C-labeled poly(ethyleneimine) it was shown that nearly a complete coverage (approximately 0.1 mg/m2) was achieved that did not desorb from the filter surface during contact with blood plasma. When the filtration was carried out with purified leukocytes in the absence of red cells, platelets, and blood plasma, the number of cells removed by modified filters (> 95%) was significantly higher as compared to the removal with unmodified filters (approximately 80%). However, no significant differences between the filters were found when the filtration was performed with whole blood. This finding was unexpected, because it was shown before that immobilization of poly(ethyleneimine) on solid polyurethane film, surfaces promoted the adhesion of leukocytes from whole blood. Apparently, the adhesive properties of the PEI diminish during filtration. Filter coating of commercial leukocyte filters composed of polyester fibers also had no effect on the removal of leukocytes from whole blood. It was postulated that morphological factors, such as filter shape, roughness, tortuosity, and porosity rather than the physicochemical properties of the filter surface influence cell adhesion to the filter surface, and through that the filtration process.

Complications and treatment of the myelodysplastic syndromes

The major complications of the myelodysplastic syndromes (MDS) are related to cytopenia and evolution to acute myeloid leukemia (AML). Hematopoietic growth factors are only of limited benefit to alleviate the cytopenia. Therapy in MDS patients over the age of 50 should aim at prolonging survival while limiting the risk of toxicity. Those with stable disease should only receive supportive care; those with progressive cytopenia should have a trial with low-dose chemotherapy. Aggressive chemotherapy should only be reserved for those failing low-dose therapy. Therapy in MDS patients under the age of 50 should aim at cure of the disease. Although aggressive chemotherapy can induce complete remission in the majority of these patients, remission is usually short. Allogeneic bone marrow transplantation is probably the only curative option in these patients and should be the treatment of choice.