Residual White Cells Research Articles

Study of single donor platelet (SDP) preparation by Baxter CS 3000 plus and Haemonetics MCS plus

Background : In plateletpheresis blood is withdrawn from a donor in anticoagulant solution and separated into components. Platelets are retained and the remaining components are returned to the individual. Methods : The present study was aimed to compare the platelet yield and collection efficiency of Baxter CS 3000 plus and Haemonetics MCS plus cell separators and to study adverse donor reactions. Donors were selected as per the set criteria for single donor platelet (SDP) preparation. Donors' samples for pre donation and post donation platelet count were collected in EDTA and for product counts in the sample pouch attached with apheresis kits. The results were obtained by haematology analyzer. Platelet yield and collection efficiency were calculated. Result : Results were tabulated for both the cell separators and analyzed. Platelet yield was marginally better with Baxter CS 3000 plus but collection efficiency was better with the Haemonetics MCS plus. Residual white cells were more in single donor platelet concentrate preparation by MCS plus. Adverse donor reactions were similar with both cell separators, in form of mild citrate toxicity and mild to moderate pain at phlebotomy site. Conclusion : Findings of the present study along with other factors such as less priming time for kit, portability of cell separator, better patient comfort owing to single arm venous access and lesser cost suggest that Haemonetics MCS plus is a better choice as compared to Baxter CS 3000 plus cell separator.

Immunomodulatory effects of blood transfusions: the synergic role of soluble HLA Class I free heavy‐chain molecules detectable in blood components

Over the past decades, the weight of the published literature demonstrates that blood transfusions can induce clinically significant immunosuppression in recipients. Several studies showed significant improved clinical outcomes in the patients receiving leukoreduced transfusions, compared with control patients who received nonleukoreduced transfusions. Moreover, the immunosuppressive potential of blood products grows with the time of their storage and becomes highest in nonleukoreduced blood products stored for a long time. The interest was previously focused on the determination of immunomodulatory soluble molecules such as soluble HLA Class I (sHLA-I) and soluble Fas ligand (sFasL) in different blood components and on the evaluation of their immunomodulatory activities. On this basis, whether soluble beta2-microglobulin free HLA Class I heavy chains (sHLA-beta2fHC) could be detected and immunochemically characterized in different blood components was evaluated. Immunomodulatory activity of detectable sHLA-beta2fHC molecules was evaluated by apoptosis inducing capacity in interleukin-2-activated antigen-specific cytotoxic T lymphocytes (CTL). Double-determinant immunoenzymatic assay indicates that sHLA-beta2fHC levels in red blood cells stored for up to 30 days and in random-donor platelets are significantly (p < 0.001) higher than in other blood components, and the immunochemical characterization suggests that the major source of sHLA-beta2fHC molecules might be the residual white cells that undergo membrane damage during storage. Finally, allogeneic CD8+ CTL apoptosis induction confirmed biofunctionality of sHLA-beta2fHC molecules. These data are comparable with those previously reported dealing with contaminant soluble molecules in allogeneic and autologous blood components, suggesting that sHLA-beta2fHC molecules could contribute to the immunosuppressive effects of blood transfusions.

Beyond leukodepletion: removing infectious prions by filtration

Beyond leukodepletion: removing infectious prions by filtration

Evaluation of different methods of leukoreduction of donor platelets to prevent alloimmune platelet refractoriness and induce tolerance in a canine transfusion model

AbstractThe effectiveness of different methods of leukoreduction in preventing alloimmune platelet refractoriness was evaluated in a canine model. Platelets from a random donor dog were administered for up to 8 weeks or until platelet refractoriness. Standard (STD; unmodified) platelets were accepted by 14% of recipients (n = 7) compared with 14% for centrifuge leukoreduced (C-LR) platelets (n = 21) and 31% for filter leukoreduced (F-LR) platelets (n = 13; no significant differences). Surprisingly, using both F-LR and C-LR platelets was highly effective (87% acceptance, n = 15). Transfusing F-LR/C-LR red blood cells (n = 4) or F-LR/C-LR plasma (n = 4), along with F-LR/C-LR platelets, did not affect platelet acceptance (100% acceptance). Overall acceptance of F-LR/C-LR platelets was 91% (n = 23; P ≤ .05 versus STD, C-LR, or F-LR platelets). F-LR/C-LR transfusions also induced tolerance to subsequent STD platelet transfusions from the same donor (82% acceptance, n = 19) as well as to donor skin grafts without recipient immunosuppression (57% acceptance, n = 7). To evaluate mechanisms of tolerance induction, F-LR/C-LR platelets were γ-irradiated. Although the γ-irradiated F-LR/C-LR platelets were uniformly accepted (n = 6), tolerance to STD platelets was lost. These data suggest that some allostimulatory white cells are filter adherent, whereas others escape filtration but can be removed by centrifugation and tolerance requires a residual functioning white cell.

White cell apoptosis in platelet concentrates.

The aim of the present study was the evaluation of the apoptosis in residual white cells (WBCs) contained in platelet concentrates (PCs) and of the relationship of this apoptosis with the concentration of inflammatory cytokines in the medium and with platelet activation. Three independent methods were used to evaluated apoptosis in WBCs present in 9 PCs, either from single donors by apheresis (SD-PCs) or from pooled buffy coats (BC-PCs). All PCs were divided in two parts, one of which was irradiated. PCs were stored up to 4 days at room temperature, and samples were withdrawn daily for analysis of apoptosis, of platelet activation (surface and soluble CD62P), and of cytokine concentration (interleukin [IL]-1alpha, IL-1beta, IL-6, IL-8, and tumor necrosis factor alpha). Apoptosis was found to occur with storage in both irradiated and nonirradiated units. Platelet activation increased with storage time and was higher in BC-PCs. The amount of released cytokines was rather variable among PC units. Only IL-8 was consistently found to increase with storage time. Apoptosis of residual WBCs occurred in PC units as a function of storage time. The amount and the time course of apoptosis seem to correlate with IL-8 release rather than with platelet activation or with the occurrence of febrile nonhemolytic transfusion reactions.

Preparation and storage characteristics of white cell-reduced high-concentration platelet concentrates collected by anapheresis system for transfusions in utero.

Important concerns with regard to in utero platelet transfusions are avoidance of volume overload and the immunomodulatory effects of residual white cells (WBCs). This study evaluated a modification of a leukocyte-reduction system (LRS, Spectra, COBE BCT) for apheresis, which collects high-concentration WBC-reduced platelets (HCPs) for in utero transfusion. The LRS procedure was modified by running the platelet collection pump at specified low flow rates (Q(col)) for the first part of the procedure, collecting HCPs by gently purging them from the LRS chamber into a designated collection bag and then restoring the original LRS procedure settings to collect a second standard apheresis platelet concentrate (PC). Two centers carried out 32 procedures. Platelet yield, residual WBCs, and in vitro platelet function studies were evaluated. Platelet concentrations in 60 mL of HCPs were predictable according to Q(col) (r(2) = 0.735). HCP yields varied from 0.9 to 3.2 x 10(11), depending on the desired final platelet concentrations in 60 mL, with an overall average of 1. 92 x 10(11) (n = 32). Apheresis PCs had a mean platelet yield of 2.9 x 10(11) (1.3-4.4 x 10(11), n = 20) and 3.9 x 10(11) (2.2-5.8 x 10(11), n = 12) at concentrations of 1.3 x 10(12) per L for single-needle and dual- needle procedures, respectively. Median WBC counts were 5.6 x 10(3) for HCPs and 2.0 x 10(4) for apheresis PCs, with >99 percent expected to be less than 1 x 10(6). HCP in vitro characteristics were equivalent to those of apheresis PCs at 24 hours after collection. In vitro performance declined over storage as a function of HCP yield. HCP pH at 22(o)C was maintained at a level of >6.2 for more than 3 days for yields >1.6 x 10(11), less than 2 days for yields 1.6 to 2.2 x 10(11), and less than 24 hours for yields >2.2 x 10(11). HCPs showed good in vitro characteristics and could be stored for 1 to 3 days, depending on the total number of platelets collected. A standard apheresis PC and an HCP requiring no secondary processing can be collected with the Spectra LRS. The platelet concentration may be determined by clinical need. HCPs meet the requirements for components that are transfused in utero.

White cell apoptosis in packed red cells.

After the removal of the buffy coat, packed red cell (RBC) transfusion units still contain white cells that may undergo apoptosis as a result of storage conditions (1-6 degrees C). The aim of the present study was the evaluation of this phenomenon in view of the possible influence it may have on febrile nonhemolytic transfusion reactions. Three independent methods (microscopy, DNA electrophoresis, and cytometry) were used to evaluate apoptosis in white cells present in 13 RBC units. Of these units, 10 had been collected into CPD/saline-adenine-glucose-mannitol and 3 into CPDA-1; each bag was split in two parts, one of which was irradiated. RBCs were stored at 1 to 6 degrees C, and samples were periodically withdrawn for study. The proliferative capacity of stored lymphocytes was evaluated after phytohemagglutinin stimulation and tritiated thymidine incorporation. Apoptosis was found to occur in both granulocytes and lymphocytes, starting from the first 48 to 72 hours of storage. The choice of the anticoagulant-preservative solution and the effect of irradiation did not influence the amount and the timing of the apoptotic phenomenon. Lymphocyte proliferative capacity was found to decrease sharply with storage time. Conditions of storage in RBCs induce consistent apoptosis in residual white cells. The possible clinical implications of the relationships between apoptosis and the induction of biologic response modifiers (that may cause interleukin-mediated febrile non-hemolytic transfusion reactions) and between apoptosis and immune reactions remain to be elucidated.

Evaluation of the Amicus Separator in the collection of apheresis platelets

A new apheresis instrument, the Amicus Separator with software versions 2.13 and 2.34, was evaluated for component yields, collection efficiency, and incidence of donor and transfusion recipient reactions. The Amicus was also compared to the Spectra Leukocyte Reduction System (LRS) with version 5 software. Single and double apheresis platelets (APs) were collected at two locations. The targeted platelet yields were 4.0 x 10(11) for single APs and 6.8 x 10(11) for double APs. One location used a double-needle procedure, and the other used a single-needle procedure. Along with 28 of the Amicus procedures (14 at each of two locations), the same donors underwent single or double AP collections on the Spectra LRS. APs were tested for platelet yields and residual white cells. APs were transfused in three hospitals. Donor and transfusion recipient reactions and technical problems were documented. The Amicus Separator efficiently collected single APs (n = 59) and double APs (n = 62) with mean platelet yields of 4.2 x 10(11) and 6.5 x 10(11), respectively. When inlet line alarms occurred in single-needle procedures, platelet yields were lower and collection times were longer. All APs were white cell-reduced below 5.0 x 10(6), and all but one AP were white cell-reduced below 1.0 x 10(6) without filtration. Component yields from the paired Amicus and Spectra LRS procedures were comparable. Collection times (excluding reinfusion/rinseback) were 20 to 23 minutes faster on the Amicus Separator. No serious donor or transfusion recipient reactions occurred. The Amicus Separator provided satisfactory platelet yields and collection efficiency, with shorter collection times than did the Spectra LRS, and it white cell-reduced components without filtration.

A multicenter evaluation of the routine use of a new white cell-reduction apheresis system for collection of platelets.

Residual white cells (WBCs) cause serious side effects in platelet transfusion. An in-line WBC-reduction system based on fluidized particle bed technology was recently developed as a modification of an existing plateletpheresis system. In an investigational phase, three flow profiles were evaluated using prototype software in five centers, each using their standard conditions. In the confirmatory phase, the released software was tested in three centers. WBCs were counted in two full Nageotte grids (dilution 1-in-5). With the prototype software, WBC levels were always below 1 x 10(6) per procedure (median, 25,000/procedure; n = 314). One profile proved to be superior to the other two with respect to platelet yield and residual WBCs, and it was incorporated in the released WBC-reduction system, together with a built-in process control. Median residual WBCs in these WBC-reduction system components not rejected by the process control were 19,000 per procedure (n = 211/225 total), with 99.5 percent of the platelet components having less than 1 x 10(6) WBCs. The protocol selected in the initial phase, now available as a WBC-reduction system, results in platelet concentrates with very low residual WBC levels. This satisfies even the most stringent criteria for WBC reduction in platelets, without the platelet loss typically seen with conventional fiber filtration.

The BEST Working Party of the International Society of Blood Transfusion: an international effort to improve the quality of blood components

The Biomedical Excellence for Safer Transfusion (BEST) Working Party of the International Society of Blood Transfusion was formed with the aim of improving the quality and safety of blood components. An outline of the aims, working methodology, and results after the first 4 years of activity of the BEST Working Party is presented. Seven studies have been performed, evaluating techniques for counting residual white cells in white cell-reduced red cells, platelet quality control, and cellular harvests in blood components prepared with different methods. Areas of possible interest in the near future include stem cells, platelet crossmatching, and virus inactivation of blood components. An important BEST feature is the sharing of information gathered through collections of large sets of data from routine settings, so as to produce a reliable picture of the "real world." Such information could prove useful to those in charge of developing recommendations and guidelines.

Quantitation of residual white cells in filtered blood components by polymerase chain reaction amplification of HLA DQ-A DNA.

Over the past several years, blood filtration technology has improved dramatically, such that currently available experimental filters are capable of reducing white cells (WBCs) in blood components to less than 0.1 WBC per microL. These residual WBC concentrations are below the sensitivity of automated cell counters, as well as of large-volume (Nageotte) hemocytometers. A quantitative polymerase chain reaction (PCR) amplification assay directed at HLA DQ-A DNA sequences has been developed for the enumeration of WBCs in filtered blood. To ensure quantitative recovery of WBCs at very low residual cell concentrations, a direct red cell lysis and WBC concentration protocol using 0.5 mL of filtered blood was perfected. Amplified product is detected by oligomer hybridization using 32P-labeled probes, with quantitation by image analysis of autoradiographic signals relative to a standardized dilution series processed in parallel. Recovery of residual WBCs in filtrates was shown to be enhanced by the addition of xenogeneic WBCs or polystyrene beads, which served as "carrier" particles during red cell lysis and wash steps. A contribution of nuclear fragments in filtered blood to PCR signal in the range of 0.01 to 0.5 WBCs per microL was observed; a modified protocol was developed to minimize this effect. Parallel analysis of spiked dilution series and evaluations of 39 red cell components filtered through commercial filters indicated good correlation between PCR and standard Nageotte counts in the range of 0.1 to 10 WBCs per microL (r2 = 0.94); only PCR was able to detect residual WBCs in filtrates from prototype 6 log10 WBC-reduction filters. This assay should prove useful for the development and quality assurance of increasingly efficient WBC-reduction filters.

Comparative analysis of six different white cell‐reduction filters for packed red cells

The reduction of white cells in blood components before transfusion by filters with at least 3 log10 depletion may prevent adverse transfusion reactions such as HLA alloimmunization, febrile reactions, transmitted infections, and immunomodulation. A new generation of filters with 4 log10 depletion is now available. The aim of this study is to compare the efficiency of white cell reduction by six commercial filters for packed red cells with 3 and 4 log10 depletion (claimed by manufacturers). The analysis of white cell concentration in the white cell-reduced units was performed by flow cytometry and with a Nageotte chamber. The last generation of filters (BPF4, RC400, R01 Plus) show mean residual white cell numbers of 0.18 +/- 0.14, 0.26 +/- 0.21, and 0.25 +/- 0.15 x 10(6), respectively, by flow cytometric analysis and 0.05 +/- 0.04, 0.18 +/- 0.15, and 0.38 +/- 0.23 x 10(6), respectively, by Nageotte chamber evaluation. The 3 log10 depletion filters (R01, Leucostop-4LT-mono, R200) have mean residual white cell numbers of 1.41 +/- 0.92, 2.4 +/- 1.99, and 1.05 +/- 0.64 x 10(6), respectively, by flow cytometric analysis and 3.56 +/- 1.7, 1.67 +/- 1.3, and 3.21 +/- 4.1 x 10(6), respectively, by Nageotte chamber evaluation. The data show that the BPF4, RC400, and R01 Plus filters are likely to be more efficient by 1 log10 reduction than the R01, Leucostop-4LT-mono, and R200 filters. The most recent generation of filters is able to deplete white cells from packed red cells by 4 log10; in particular, with one of the filters, the residual WBC content was less than 0.5 x 10(6) per unit in all experiments, while two other filters reached that level in 9 of 10 experiments.

Effects of 3‐5 log10 pre‐storage leucocyte depletion on red cell storage and metabolism

A new, in-line high-efficiency 3-5 log10 leucodepletion filter system (Leukotrap RC system) was used to investigate the effect of pre-storage white cell removal on the quality of AS-3 red cell concentrates stored for 42 d at 4 degrees C. Median residual white cell content was 4 x 10(5) when filtration was performed at 22 degrees C within 8 h of phlebotomy (n = 20) and 3.2 x 10(4) when filtration was performed at 4 degrees C 12-24 h after phlebotomy (n = 24). None exceeded 1 x 10(6) WBC per red cell product. Filtration was rapid (median 28 min), and red cell loss averaged (mean +/- 1 SD) 6.4 +/- 0.7%. In a paired study design, post-transfusion recoveries of 42 d stored red cells in the filtered units averaged 84 +/- 6% v 82 +/- 8% for unfiltered units (P < 0.05) and post-storage haemolysis. ATP, osmotic fragility, K+ and pH were significantly (P < 0.05) better in the filtered units. Reduced glycolytic activity was also observed in the filtered units, and there was a correlation between osmotic fragility, glucose consumption, and lactate produced in standard units that was not present in leucodepleted units. In conclusion, this study suggests that leucodepletion of AS-3 red cell concentrates prior to storage results in better maintenance of the integrity of the red cell membrane with reduced glycolytic activity. There was a modest improvement in post-infusion viability sufficient to offset the filtration-induced loss and to result in an equivalent red cell product.

Multicenter Evaluation of Methods for Counting Residual White Cells in Leukocyte-Depleted Red Blood Cells

Two wet workshops were conducted involving 20 laboratories to determine optimum methods for counting residual white blood cells (WBC) in leukocyte-depleted red blood cells (RBC). In both studies, calibration samples containing known concentrations of WBC were prepared by diluting 1-day-old EDTA blood in RBC virtually free of WBC. Study No.1 was aimed at determining the lower limit of detection and at examining advantages and disadvantages of two methods based on flow cytometry (FC) and on the Nageotte chamber (NC), respectively. This study showed that the lower detection limits for FC and NC were 0.1 and 1WBC/µl, respectively. Methods based on FC showed less variability at 0.1-1 WBC/µl but were equal in performance to counting procedures based on the NC above lWBC/µl. We then designed study No. 2 to evaluate three different protocols using the NC. In protocol 1, samples were diluted 1:10 with Plaxan and withTiirk’s solution; in protocol2 a mixture of Türk’s solution and Zap-oglobin, a reagent used in manual hemoglobin determinations, was used to dilute the samples 1:5; and protocol 3 involved initial 1:10 dilution of a 1-ml sample with Plaxan followed by WBC concentration into the original 1-ml volume by centrifugation. In each participating laboratory, two technologists independently processed the samples and read the results with an NC. Plaxan and Tiirk’s solution gave comparable results. Interobserver variability was not critical to the results. All three NC methods were valid for counting at concentrations of ≥ 1 WBC/µl. Protocol 3 showed the greatest precision, allowing the measurement of WBC at concentrations of 0.1-1/µl (30,000-300,000 WBC in a 300-ml RBC unit) with a coefficient of variation of approximately 50% or less. Based on these results the Biomedical Excellence for Safer Transfusion (BEST) Working Party considers all three NC protocols adequate for the routine evaluation of current leukocyte removal filters, i.e. at levels ≥ 1WBC/µl. The evaluation of new and more effective filters and validation of filter performance may require techniques with a greater precision at counts below 1 WBC/µl, such as protocol 3. For the latter purposes FC is also applicable. Because the counting techniques were not validated using stored blood, these conclusions only apply to samples obtained from blood stored for 1 day.

Multicenter Evaluation of Methods for Counting Residual White Cells in Leukocyte‐Depleted Red Blood Cells

Two wet workshops were conducted involving 20 laboratories to determine optimum methods for counting residual white blood cells (WBC) in leukocyte-depleted red blood cells (RBC). In both studies, calibration samples containing known concentrations of WBC were prepared by diluting 1-day-old EDTA blood in RBC virtually free of WBC. Study No. 1 was aimed at determining the lower limit of detection and at examining advantages and disadvantages of two methods based on flow cytometry (FC) and on the Nageotte chamber (NC), respectively. This study showed that the lower detection limits for FC and NC were 0.1 and 1 WBC/microliters, respectively. Methods based on FC showed less variability at 0.1-1 WBC/microliters but were equal in performance to counting procedures based on the NC above 1 WBC/microliters. We then designed study No. 2 to evaluate three different protocols using the NC. In protocol 1, samples were diluted 1:10 with Plaxan and with Türk's solution; in protocol 2 a mixture of Türk's solution and Zap-oglobin, a reagent used in manual hemoglobin determinations, was used to dilute the samples 1:5; and protocol 3 involved initial 1:10 dilution of a 1-ml sample with Plaxan followed by WBC concentration into the original 1-ml volume by centrifugation. In each participating laboratory, two technologists independently processed the samples and read the results with an NC. Plaxan and Türk's solution gave comparable results. Interobserver variability was not critical to the results. All three NC methods were valid for counting at concentrations of > or = 1 WBC/microliters.(ABSTRACT TRUNCATED AT 250 WORDS)

White cell‐reduced red cells prepared by filtration: a critical evaluation of current filters and methods for counting residual white cells

White cell (WBC) reduction, red cell (RBC) recovery, and filtration time were determined in 1-day-old standard and buffy coat-depleted RBCs filtered in the laboratory through six commercial filters for WBC reduction. Residual WBCs were counted with a Bürker chamber (BC), with a Nageotte chamber (NC), and by flow cytometry (FC). Results show that BC counts were 0 in several cases in which WBCs were detected with NC and FC, which indicated that the traditional BC method is too insensitive in use with currently available filters. Calibration curves performed by FC and with NC with samples containing known concentrations of WBCs from 1000 to 1 per microL showed that both FC and NC detected, on average, 67 percent of WBCs present in the samples (efficiency). However, the efficiency of FC showed small variability (61-70%) at different WBC levels, whereas the variability with NC was large (39-91%). This greater variability prevented the correction of NC counts by using a single factor and indicated difficulty in NC standardization. Therefore, because our main aim was to compare different filters rather than to define absolute levels of WBC contamination, uncorrected FC and NC counts were chosen to be reported. True WBC counts per unit should not exceed values that can be obtained by dividing uncorrected counts by the lowest efficiencies (61% for FC and 39% for NC). Uncorrected NC and FC counts were below 2 x 10(6) per unit in all units processed through three of the filters and below 5 x 10(6) per unit in all units processed through the other three.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of prestorage white cell reduction on the function and viability of stored platelet concentrates.

The role of residual donor white cells (WBCs) in producing the storage lesion of platelets used for transfusion was studied. The effect of prestorage WBC reduction on in vitro and in vivo measurements of the quality of stored platelet concentrates (PCs) was examined by using a newly developed WBC-reduction filter capable of preparing PCs with a mean residual WBC concentration of less than 1 per microL. For in vitro studies, a triplet study design was used, in which WBC-reduced PCs were matched to standard PCs and to WBC-enriched PCs obtained from the same donor at the same phlebotomy. Twelve donors were studied. Prestorage WBC reduction resulted in a higher pH and pO2 and a lower pCO2 than in standard PCs. In accord with previous in vitro studies, a significant rise in plasma glycocalicin and lactate dehydrogenase was measured during storage, but the levels were not significantly different in WBC-reduced PCs and standard PCs. Platelet aggregation and ATP release in response to graded doses of thrombin was similar in WBC-reduced and standard PCs. In vivo recovery and survival studies were comparable in WBC-reduced and standard PCs. Although the residual donor WBC content of PCs has a significant impact on storage pH, pO2, and pCO2, prestorage WBC reduction does not affect platelet structure, function, or viability as assessed by in vitro or in vivo measurements.

Phenotypic characterization of white cells in white cell-reduced red cell concentrate using flow cytometry.

The residual white cell (WBC) content of donated units of red cell concentrate rendered WBC-reduced by filtration through commercially available polyester filters was quantified and phenotypically analyzed. All studies were performed by flow cytometery. Quantification studies were performed with a DNA/RNA fluorophore, propidium iodide. WBC subset analyses were performed with fluorescence-labeled monoclonal antibodies directed against various cluster differentiation (CD) loci. The results indicate that the filter removes in excess of 3 log10 total WBCs from the red cell components and depletes granulocytes to or beyond the specific assay's sensitivity of 3 log10. Total T and B cells, T4 and T8 lymphocytes, and monocytes are reduced by approximately 4 log10. These analyses provide plausible explanations for the clinical success of the filter and suggest other potential applications.

Removal of white cells from red cells by transfusion through a new filter

The effectiveness of a new filter (RC100) for the preparation of white cell-depleted red cells (RBCs) at the bedside was evaluated in vitro and in vivo using three RBC products: standard RBC concentrate (CPDA units), RBCs suspended in saline-adenine-glucose-mannitol additive solution after the removal of plasma (SAGM units), and RBCs suspended in SAGM after the removal of plasma and buffy coat (SAGM-BC units). Median RBC recovery was at least 92 percent when 2 units were administered through one filter; median values for residual white cells and platelets were less than or equal to 20 x 10(6) and less than or equal to 2.5 x 10(9) per 2 units, respectively. The in vivo study was carried out in 80 multiply transfused patients with thalassemia, 35 of whom had experienced frequent nonhemolytic transfusion reactions when given standard or buffy coat-free RBCs. During the 6-month study, each patient was given two transfusions of each type of RBC product One febrile nonhemolytic transfusion reaction occurred in each of two patients receiving SAGM-BC units, but in no other case. If the flow rate is not reduced, the median transfusion time is 35 minutes per CPDA unit and 15 minutes per SAGM and SAGM-BC unit. It is concluded that the transfusion of RBCs through the RC100 is a simple and effective procedure to administer white cell-depleted RBCs prepared at the bedside.

Preparation of white cell‐depleted blood. Comparison of two bedside filter systems

Numerous techniques have been established for preparing white cell-poor blood, such as centrifugation, sedimentation, freezing, and filtration. All of these methods have disadvantages that restrict their practical use: they are time-consuming, they require the facilities of a blood bank, and the white cell-poor units cannot be stored. Therefore tests have been performed on two filter systems that make possible the depletion of white cells directly at the bedside. Both filters have a high white cell-removal rate. The number of residual white cells in 1 unit of packed red cells was calculated as 1.08 +/- 0.53 x 10(7) in one system and 1.54 +/- 0.71 x 10(7) in the other. The filters do not affect the filtered red cells. Pressure filtration is performed without significant loss of efficiency. One of the systems can filter 2 units via one filter; however, handling the filters is tedious, and both filters are characterized by a low red cell recovery. Despite these disadvantages, the tested filter systems provide an effective device for preparing white cell-poor blood at the bedside. They are a suitable alternative to the conventional methods.