WBC filtration of whole blood after prolonged storage at ambient temperature by use of an in-line filter collection system

BACKGROUND: Before-storage WBC reduction by filtration appears to be an effective way to prevent transfusion-associated complications. It also has superiority over WBC reduction at the time of transfusion (bedside), due to the many variables associated with such practice and the difficulty in performing adequate quality control. To determine the adaptability of collection systems containing in-line filters to the current blood collection strategy, the feasibility, efficiency, and quality of before-storage WBC reduction of whole blood (WB) units were evaluated, following their prolonged storage at ambient temperature prior to component preparation, by use of an integral in-line filter. STUDY DESIGN AND METHODS: Blood was collected from random donors into quadruple blood pack units with an integral in-line filter and divided into three groups, according to storage conditions. WBC reduction was performed at room temperature, on WB units after storage at ambient temperature either for less than 8 or up to 18 hours on 1,4-butanediol cooling trays or for 18 hours in the cold. RESULTS: All the filtration procedures met the AABB threshold of less than 5 x 10(6) residual WBCs per unit and the European requirements for WBC counts of less than 1 x 10(6) WBCs per unit. The average filtration time was less than 22 minutes in all units studied. Filtration time and blood flow rate were both significantly longer, and RBC loss was significantly higher in WB units that were filtered after prolonged storage in the cold. CONCLUSIONS: Adequate before-storage WBC reduction can be achieved when performed on WB units, which were stored at ambient temperature for 18 hours, by use of an in-line filtration system. The procedure, performed under relatively simple logistics, results in good-quality, standard components, which require no further modifications when supplied to the transfusion services.     

Stored packed red blood cells contain a procoagulant phospholipid reducible by leukodepletion filters and washing.

BACKGROUND: Ageing RBC gradually increase the exposure of phosphatidylserine (PS) on their surface, due to loss of membrane asymmetry. PS expression on red cells is not normally a significant factor in the hemostatic process, because aged RBC are rapidly cleared from the circulation. We propose that the presence of many altered red cells during massive transfusion can lead to increased procoagulant activity similar to what is seen in disease states where it is known to play a pathophysiologic role in microvascular disease. STUDY DESIGN AND METHODS: Procoagulant activity of phospholipid generated during storage of PRBC was evaluated using PRBC's as the only source of phospholipid in the determination of modified Russell's viper venom times of 10 PRBC units in which half of each unit was left unfiltered and half of each unit filtered. Florescent labeled annexin V binding by PRBC was also assessed by flow cytometry over time in storage. The effect of washing and filtration on these parameters was also determined. RESULTS: As time of storage increased, the Russell's viper venom time of both the unfiltered and filtered units shortened (p<0.01). There was a significant lengthening of the Russell's viper venom time at all time points measured when unfiltered units were compared to filtered units (p<0.01). In both unfiltered and filtered units, with increased length of storage, there was a gradual increase in the percentage of cells or particles binding annexin V (p<0.01). Filtration resulted in a significant reduction in the percentage of cells or particles binding annexin V at all time points measured (p<0.01). The effect of washing of PRBC units on the RVVT was assessed for unfiltered and filtered units on day 42. Washing resulted in a significant reduction of the RVVT in both unfiltered and filtered groups (p<0.01). CONCLUSIONS: Levels of annexin V binding and procoagulant phospholipid activity similar to levels seen in disease states associated with significant vasoocclusive pathophysiology were found toward the end of the storage period of PRBC units. It was possible to reduce both of these parameters by leukodepletion at collection, and with washing of PRBC at the end of storage. Filtration at collection resulted in a 67% increase in RVVT over unfiltered units by day 42 of storage. On day 42 of storage, washing of filtered units resulted in a 21% increase in RVVT, and washing of unfiltered units resulted in a 34% increase in RVVT. The effects seen with filtration and washing were additive suggesting that in spite of filtration at collection, deterioration of cells continues based on age since further removal of phospholipid can be induced with washing of filtered units on day 42.     

Leukodepletion filters reduce Leishmania in blood products when used at collection or at the bedside

BACKGROUND: Leishmania is an intracellular parasite of monocytes transmissible by transfusion. The feasibility of reducing Leishmania with leukodepletion filters was studied. At collection, infected blood contains the amastigote form of Leishmania within monocytes. Amastigotes cause the rupture of monocytes releasing free amastigotes that convert to promastigotes, which exist extracellularly at blood storage temperatures. Leukodepletion filters were tested at various time points in this process. STUDY DESIGN AND METHODS: Blood products were infected with Leishmania organisms and then filtered with whole-blood filters at collection, with bedside filters after storage, and to determine whether free promastigotes could be eliminated. RESULTS: Filtration at collection reduced Leishmania by 3 to 4 log or to the level of detection. Filtration of infected red cells after 2 weeks of storage showed a reduction of Leishmania by 4 log. Filtration resulted in a 6- to 8-log reduction in promastigotes either in the presence or in the absence of white cells within the filter. CONCLUSION: Filtration at the time of collection and after storage of Leishmania-infected blood resulted in a substantial reduction of free and intracellular organisms. There is currently no donor screen for Leishmania. Until adequate testing is developed, the use of leukodepletion filters could add to the safety of the blood supply.     

Release of PMN elastase, TGF-beta1 and neopterin during blood storage; unfiltered versus filtered blood.

Release of inflammatory mediators from blood cells during prestorage leukocyte filtration may result in recipient immune suppression. To investigate the effects of prestorage leukocyte filtration on the quality of blood components, twenty-four blood units were collected from healthy donors and randomised into 3 groups. Eight units were stored as whole blood, eight units were separated into plasma, red blood cells (RBC) and buffy coat and eight units were collected and filtered through the ASAHI RZ 2000 leukocyte filter and separated into plasma and RBC. The units were stored for 35 days. Samples were collected weekly for analyses of polymorphonuclear elastase (PMN elastase), transforming growth factor-beta1 (TGF-beta1) and neopterin. PMN elastase and neopterin increased during storage of whole blood and RBC. From the beginning and throughout storage, PMN elastase was increased in filtered plasma as compared with unfiltered plasma. Filtration per se did not influence the neopterin concentration in plasma or RBC. TGF-beta1 increased in plasma and RBC during storage. In filtered plasma, an elevation of the TGF-beta1 concentration was observed from the start of storage. The TGF-beta1 levels were higher in filtered plasma compared with unfiltered plasma. Prestorage leukocyte filtration increased the release of PMN elastase and TGF-beta1 in plasma and RBC.     

Infusion of P-Capt prion-filtered red blood cell products demonstrate acceptable in vivo viability and no evidence of neoantigen formation

BACKGROUND: Transmission of variant Creutzfeldt‐Jacob disease (vCJD) is a major concern in blood transfusion. The P‐Capt filter has been shown to remove around 4 log ID₅₀ prion infectivity from prion‐spiked human red blood cells (RBCs). STUDY DESIGN AND METHODS: Two independent, single‐center, randomized, open‐label studies were designed to analyze the safety of P‐Capt–filtered RBCs. RBCs prepared from leukoreduced whole blood from 43 eligible subjects were randomly assigned to P‐Capt filtration and/or storage in plasma or SAGM and stored for 28 or 42 days. Stored RBCs were analyzed for in vivo 24‐hour recovery, hemolysis, metabolic variables, blood group antigen expression, neoantigen formation, and safety after autologous infusion. RESULTS: Mean P‐Capt filtration times for leukoreduced RBCs were 41 (SAGM) to 51 (plasma) minutes. Thirteen of 14 subjects receiving P‐Capt–filtered RBCs had 24‐hour RBC recoveries of 75% or more after 42‐day storage, with a mean hemolysis of less than 0.6%. No loss of RBC antigen expression or formation of neoantigens was observed. In both studies, RBCs had white blood cell counts of less than 1 × 10⁶/unit after leukofiltration. P‐Capt prion filtration provided an additional greater than 0.8 log leukoreduction. No serious or unexpected adverse events were observed after infusion of P‐Capt–filtered full‐volume RBC units. CONCLUSIONS: P‐Capt–filtered, stored RBCs demonstrated acceptable viability and no detectable neoantigen expression, immunogenic responses. or safety issues after infusion of a complete unit. The additional filtration time and modest reduction in RBC content are within acceptable levels for implementation in countries with transfusion transmission of vCJD.     

Neutrophil priming, caused by cell membranes and microvesicles in packed red blood cell units, is abrogated by leukocyte depletion at collection.

BACKGROUND AND OBJECTS: Lipids with platelet activating factor (PAF)-like activity in supernatant of packed red blood cells (PRBC) cause priming of the neutrophil respiratory burst. This effect increases with length of storage. Washing of PRBC has been considered as a means to eliminate this effect; however, the role of the cellular component was not evaluated independently of the supernatant. The source of the inflammatory lipids of the supernatant is likely to be cell membranes altered during ageing in storage and therefore, washing will not eliminate neutrophil priming caused by transfusion of aged PRBC units. The ability of washed PRBC to prime mononuclear cells for another known effect of PAF, the production of IL-8, and the probability that this lipid activity is present on microparticles in PRBC supernatant were also investigated. MATERIALS AND METHODS: At collection 10 units of whole blood were split into two equal aliquots one filtered and one unfiltered. PRBC were prepared and stored at 4 degrees C in CPD-AS5. Each week, fresh neutrophils were incubated with samples of washed PRBC and fixed. Change in CD11b, a marker known to increase on the surface of primed neutrophils, was determined by flow cytometry. To determine whether neutrophil priming ability of PRBC supernatant is contained on microvesicles, centrifuged and uncentrifuged supernatant samples were incubated with fresh neutrophils and change in CD11b expression was determined. Plasma IL-8 levels were also measured after exposure of monocytes from fresh whole blood to filtered and unfiltered washed PRBC with and without the addition of fMLP. RESULTS: Washed PRBC caused a 50-116% increase in CD11b neutrophil surface expression over baseline expression. Filtration of whole blood at collection reduced this CD11b up-regulation by 25-34%. Reduction of priming ability by filtration began on the day of collection and persisted for the storage life of the units. Centrifugation resulted in a reduction of CD11b up-regulation of 11-28% compared with unspun supernatant. Incubation of unfiltered PRBC resulted in priming of mononuclear leukocytes for IL-8 production with a 73-109% increase over baseline, but no increase over baseline was seen for incubation with filtered blood. CONCLUSION: Washing does not eliminate the ability of PRBC units to prime neutrophils and mononuclear cells, because the cellular component of PRBC, in addition to the supernatant, induces priming. Leukodepletion filters significantly reduce these effects compared with unfiltered PRBC. The in vitro beneficial effect of filtration lasts for the shelf life of 42 day units. The ability of PRBC supernatant to prime neutrophils is present on microvesicles.     

Leukoreduction filtration of whole-blood units from sickle trait donors: effects of a metered citrate anticoagulant system

BACKGROUND: Polymerization of hemoglobin (Hb) S is exacerbated by acidic and hyperosmotic citrate anticoagulant solutions and often results in occlusion of leukoreduction filters by red blood cells (RBCs) from sickle cell trait (Hb AS) donors. This study evaluates a blood collection instrument that adds citrate anticoagulant in a metered fashion, thus mitigating adverse citrate effects. STUDY DESIGN AND METHODS: Collection of whole blood by a metered anticoagulant system was compared to traditional phlebotomy in 12 Hb AS and 12 non-sickle trait (Hb AA) donors. Each donated twice; on one occasion, units were filtered after 4-hour storage at 20 to 24 degrees C, and on the other, units were stored at 1 to 6 degrees C for 24 hours before filtration. RESULTS: Filtration times, RBC recoveries, and residual white blood cell (WBC) counts met defined criteria more often in Hb AS units collected by a metered anticoagulant system (9 of 12, 8 of 12, and 4 of 12, respectively) compared to traditional phlebotomy (1 of 12, 2 of 12, and 0 of 12, respectively). Overall, Hb AS units filtered better after storage at 1 to 6 degrees C for 24 hours, with units collected by a metered anticoagulant system undergoing filtration most effectively (5 of 6 had >85% RBC recovery, 3 of 6 had <5 x 10(6) residual WBC). Units exhibited similar changes in RBC storage parameters. CONCLUSION: Use of a metered anticoagulation instrument demonstrates potential for successful leukoreduction and acceptable storage of Hb AS units; however, the system needs further modifications and improvements before it can be utilized to collect and leukoreduce Hb AS blood.     

Safety and efficacy of unmodified whole blood vs. buffy coat-depleted red cell concentrates in autologous transfusion of elective orthopaedic surgery patients

Storing autologous blood as whole blood (WB) has been proposed for increasing the cost-effectiveness of preoperative autologous blood donation programmes. However, experimental data suggest that autologous leucocytes might lead to immunomodulation similar to the effect attributed to allogeneic leucocytes. In a retrospective analysis, the postoperative outcome of 120 patients undergoing elective orthopaedic surgery and having donated up to two units of autologous WB (AWB) was compared with that of a control group of 52 patients, whose autologous donation had been processed into buffy coat-depleted red cell concentrates (RCC). At least one autologous unit, but no allogeneic units, had been transfused in all analysed patients. Donation schemes were equally efficacious in both groups. There was no significant difference in postoperative infection rates between the two groups. Overall rates were 7.7% in the RCC group and 8.3% in the WB group. Surgical, thromboembolic and other recorded complications, length of postoperative hospital stay and days of the use of antibiotics were also not significantly different between the two groups. The results of this study suggest that transfusion of up to two units of unmodified AWB is as efficacious as the transfusion of autologous RCC and does not negatively influence the postoperative outcome in elective orthopaedic surgery.     

Longitudinal monitoring of WBC subsets in packed RBC units after filtration: implications for transfusion transmission of infections

BACKGROUND: Specific subsets of peripheral blood WBCs are reservoirs for infectious agents, such as CMV and EBV, and can serve as vectors for transfusion transmission of these agents. While filter WBC reduction has been used to prevent transfusion transmission of infections, its effectiveness has not been documented for many infectious agents and in some instances may be difficult to demonstrate in clinical trials. Because the effectiveness of filtration depends on the number of infected WBCs remaining at transfusion, WBC subpopulations in packed RBC units were quantitated after filtration and storage. STUDY DESIGN AND METHODS: Packed RBC units (n = 14) were filtered and stored at 4(o)C for 42 days or were stored without filtration. Serial samples were subjected to flow cytometric immunophenotyping of WBC subsets: neutrophils, monocytes, CD4+ and CD8+ T cells, B cells, and NK cells. RESULTS: Filtration produced a mean reduction in total WBCs of 3.2 log. Monocytes, lymphocytes, and neutrophils were reduced by 4.1, 3.8, and 2.5 log, respectively. Lymphocyte subsets also demonstrated differential reduction with filtration. All WBC subsets showed ongoing loss during storage. CONCLUSIONS: Monocyte and lymphocyte subsets are removed most effectively by prestorage filtration. Postfiltration storage leads to further significant reductions in WBC subsets. The implications of these findings for the mitigation of transfusion transmission of infection are discussed.     

Variables determining blockage of WBC-depleting filters by Hb sickle cell trait donations

BACKGROUND: Sickle cell trait donations can block leukodepletion (LD) filters or fail to LD, but the variables affecting blockage are unclear. STUDY DESIGN AND METHODS: To identify critical variables for further study, the relationship was investigated between filter blockage and donor characteristics, processing conditions, PLT and coagulation system activation, and microvesicle formation in donations with (n = 63) and without (n = 40) sickle trait. With eight filter types whole blood was LD either at ambient temperature on Day 0 or after overnight 4 degrees C hold. Markers of PLT activation (CD62P and CD63 expression and soluble CD62P) and coagulation activation (activated FXII and prothrombin fragment 1 + 2 [F1 + 2]), RBC microvesicles, blood gases, and residual WBCs were measured. RESULTS: All Day 0 filtrations blocked (n = 7). On Day 1, no filter tested was 100 percent successful, with most achieving an approximate 50 percent success rate. Two filters blocked consistently and an additional filter did not block, but resulted in 50 percent of units with high residual WBC counts (30 x 10(6)-394 x 10(6)/unit). Day 1 filtration was not improved if performed at 4 degrees C. Donor RBC variables and prefiltration measures varied little between blocked and successful filtrations except pO2, where 9 of 17 blockages had a pO2 of less than 5.0 kPa, compared with 0 of 13 completed filtrations. F1 + 2 levels increased after filtration in sickle trait units, a consequence of slow flow rate. CONCLUSION: Filter blockage in sickle trait donors cannot be predicted by donor characteristics or filter type and is not related to PLT or coagulation activation, but can be reduced by storing units at 4 degrees C before filtration.     

In vivo and in vitro characteristics of double units of RBCs collected by apheresis with a single in-line WBC-reduction filter

BACKGROUND: A novel apheresis procedure for a blood separator (MCS+, Haemonetics) enables the collection of 2 WBC-reduced RBC units in a single donation by using one disposable set with one in-line WBC-reduction filter (RC2H, Pall Corp.). The objective of this study was to evaluate the filtration performance in connection with different prefiltration RBC storage conditions and with the in vitro and in vivo storage quality of the filtered units. STUDY DESIGN AND METHODS: Sixty-six 2-unit RBC collection and gravity-filtration procedures were completed at three sites, resulting in 132 RBC units. Filtration of the double RBC units was performed at room temperature (RT) within 8 hours of collection (n = 36) and under refrigeration (1-6 degrees C) for up to 24 hours (n = 10) and 72 hours (n = 20) before filtration. RBC quality was compared to that of nonfiltered apheresis RBC units (n = 10). RESULTS: Median filtration time was 6.5 and 14 minutes for units stored at RT and under refrigeration, respectively. All 132 RBC units had residual WBC counts <0.4 x 10(6). The refrigerated units showed a greater mean log reduction in WBCs: 5.06 +/- 0.16 (24 hour) and 4.74 +/- 0.48 (72 hour), respectively, than did RT units: 4.47 +/- 0.28 (p<0.05). RBC loss was less than 12 percent in all cases (mean, 7.8 +/- 1.8%). Minimal differences in volume were observed between the paired RBC units. In vitro RBC storage characteristics of the filtered units were as expected and similar to those of the nonfiltered units. For RBC units held at RT (n = 24), the mean in vivo 24-hour recovery was 81.8 +/- 8.4 percent (double-label). CONCLUSION: Satisfactory filter performance in terms of WBC removal and RBC loss was observed with all 66 procedures, irrespective of storage conditions before filtration.     

Stablization of von Willebrand factor in banked blood by leucocyte depletion

Summary: The von Willebrand factor (vWf) activity, as measured by the ristocetin co-factor (vWf:RCo) and collagen binding (vWf:CBA) assays, declined progressively in standard blood units stored at 4°C after a 2-day storage period. This loss of activity was accompanied by a loss and degradation of high molecular weight (HMW) vWf multimers. In studies using a paired design, filtration of blood with a high efficiency leucocyte-removal filter, prior to storage at 4°C, led to significantly improved maintenance of vWf:RCo and vWf:CBA compared with unfiltered units ( P , < 0·01 after 8 days). Loss and degradation of HMW vWf decreased when blood was filtered prior to 4°C storage. Filtration had no effect on vWf-associated activities when blood was stored at 22°C for 10 days.
These results indicate that part of the storage lesion of vWf in banked blood is due to leucocyte-mediated removal and degradation of HMW vWf. This has implications when specifying plasma for the production of vWF concentrates and may also play a role in the haemostatic lesion associated with massive transfusion of stored blood.     

Leukodepletion of autologous whole blood has no impact on perioperative infection rate and length of hospital stay

BACKGROUND: Several mechanisms have been proposed as possible causes of transfusion‐related immunomodulation (TRIM) after allogeneic transfusion. If one of these mechanisms, the release of mediators of immunity and inflammation (“biologic response modifiers”[BRMs]) from disintegrating blood cells during storage of blood products, really causes TRIM, it should in principle also occur after autologous transfusion. As a consequence, prestorage leukoreduction of autologous blood should be able to prevent the clinical consequences of TRIM after autologous transfusion. STUDY DESIGN AND METHODS: This hypothesis was investigated in a multicenter, double‐blind, randomized controlled trial. A total of 1089 patients scheduled for total hip arthroplasty and eligible for preoperative autologous blood donation were randomly assigned to receive autologous whole blood (AWB) either unmodified or leukoreduced when transfusion was indicated. RESULTS: Neither the primary study outcome, that is, the overall postoperative infection rate (17.3% vs. 17.6%, p = 0.59), nor several secondary outcomes like median length of hospital stay (14 days vs. 14 days, p = 0.17) were significantly different between groups, whether analyzed according to the intention‐to‐treat principle or “as treated.” CONCLUSION: This trial provides strong evidence, from clinically relevant outcome data, that leukoreduction of AWB does not improve postoperative patient outcome and that the release of BRMs from disintegrating blood cells during storage cannot explain the immunomodulatory effect of blood transfusion.     

Preparation of white cell-reduced red cells by filtration: comparison of a bedside filter and two blood bank filter systems

BACKGROUND: Concern has been raised about the quality of white cell (WBC)-reduced red cells (RBCs) obtained by bedside filtration. The bedside performance and workload of a routine bedside filter have been compared to the laboratory performance and workload of two blood bank filter systems. STUDY DESIGN AND METHODS: Buffy coat-depleted saline- adenine-glucose-mannitol (SAGM) RBCs (90 units) were prepared. Thirty units were filtered with each of the two blood bank filter systems, and 30 units were filtered (but not transfused) with the bedside filter in a clinical department after 8 to 24 days of storage. The RBCs lost and the postfiltration WBC content (Nageotte chamber) were determined for all filtered units, and the workload associated with filtration by each of the filter systems/filter was assessed. Units with a postfiltration content of > or = 2 × 10(6) WBCs were regarded as filtration failures. RESULTS: Four (13%) of the 30 units filtered at the bedside were filtration failures, compared to no failures with either of the blood bank filter systems. In addition, the median WBC content (0.14 × 10(6)) of the units filtered at the bedside (2 units/filter) was significantly higher than that of the units filtered in the blood bank (0.05 × 10(6)). The RBC loss was significantly higher with the filter systems than with the bedside filter, provided 2 units per filter were processed with the latter. The timed workload of the filter systems was 45 to 75 minutes per 12 units, which was similar to the time required for bedside filtration. CONCLUSION: Bedside filtration of 2 units of stored buffy coat-depleted SAGM RBCs per filter resulted in a higher incidence of filtration failure and higher postfiltration WBC content than did laboratory filtration of 1 unit of fresh buffy coat-depleted SAGM RBCs per filter with either of two blood bank filter systems.     

Complement activation in prestorage leucocyte-filtered plasma

Complement activation and generation of pro-inflammatory cytokines occur during storage of blood components. Prestorage leucocyte filtration of platelet concentrates and red cells diminishes the accumulation of leucocyte-derived cytokines during storage, however, transfusion reactions are not eliminated. We investigated inflammatory mediator release during storage of plasma and whole blood and the effect of prestorage leucocyte filtration of plasma. Twenty-four blood units were collected from healthy blood donors and stored for 35 days. Eight units were stored as whole blood, eight units as plasma and eight units as prestorage filtered plasma. Samples were collected weekly for analyses of potassium, leucocytes, free plasma haemoglobin, complement activation (C3a and SC5b-9) and pro-inflammatory cytokines [interleukin (IL)-6, IL-8 and tumor necrosis factor (TNF)-alpha]. Elevated levels of C3a and SC5b-9 were registered in filtered plasma, from the beginning of storage. C3a levels increased during storage. There was a higher rate of change during storage in C3a (P < 0.01) and SC5b-9 (P < 0.05) in plasma compared with filtered plasma. Interleukin (IL)-8 is released in whole blood. The cytokine levels generated in plasma and filtered plasma were low. Complement activation is present in whole blood, plasma and filtered plasma during storage. Prestorage filtration of plasma activates the complement cascade but does not influence cytokine generation.     

Evaluation of a new whole-blood filter that allows preparation of platelet concentrates by platelet-rich plasma methods

BACKGROUND: A novel WBC-reduction in-line whole-blood (WB) filter that does not retain platelets was evaluated to assess the filtration performance and, after processing WB by the platelet-rich plasma (PRP) method, to analyze the storage quality of filtered platelet concentrate (PC) units. STUDY DESIGN AND METHODS: To analyze the filter retention, blood was collected from random donors into quadruple blood packs with an integral in-line filter (Imuflex WB-SP, Terumo; n = 25) or in standard triple bag systems (n = 30). To assess the in vitro storage characteristics of platelets, 26 WB units were pooled in pairs and redistributed into 13 units that underwent WBC reduction and 13 units that were not WBC reduced. In all cases, WB was separated into RBCs, PCs, and plasma by the PRP method and platelet function was compared. RESULTS: The filtration procedure led to RBC and PC WBC-reduced products that met the AABB and European requirements. The average filtration time was 30 minutes, the filter retained about 45 mL of WB, and there was no further loss of RBCs during the fractionation procedure. In vitro PC storage characteristics of the filtered units were similar to those of the nonfiltered units. CONCLUSION: A 4- and 3-log WBC reduction was observed in RBC and PC units that were produced by the PRP method, with a mean residual WBC content of 0.24 +/- 0.38 x 106 and 0.02 +/- 0.03 x 106 per unit, respectively. The procedure, performed under relatively simple logistics, results in good-quality, standard components that may reduce costs and ease the process of WBC reduction in transfusion services.     

Prestorage white cell reduction in saline-adenine-glucose-mannitol red cells by use of an integral filter: evaluation of storage values and invivo recovery

BACKGROUND : Prestorage white cell (WBC) reduction in blood components may decrease the incidence of adverse reactions and improve component quality. A bottom-and-top system with an integral third-generation WBC- reduction filter has been studied. STUDY DESIGN AND METHODS : Whole blood was collected from 30 healthy donors: from 20 by using a blood container system with an integral filter and from 10 controls by using a standard blood container system. Ten test units were buffy coat- depleted, stored for 72 hours at 4 degrees C, and then filtered, while an additional 10 test units were buffy coat-depleted and filtered at room temperature within 8 hours of collection. All units were stored at 4 degrees C for 42 days and sampled weekly. RESULTS : The mean WBC content of the 72-hour, 4 degrees C units was 0.33 × 10(6), that of the room-temperature units was 2.6 × 10(6), and that of the buffy coat- depleted controls was 460 × 10(6) (p < 0.0005). No significant differences were found among lactate, glucose, sodium, potassium, and plasma hemoglobin levels in the three groups. ATP and 2,3 DPG levels were significantly better preserved in control units than in 72-hour, 4 degrees C units (p = 0.016 and p = 0.032, respectively), but not better than in the room-temperature units. Significant differences were observed between pH values in filtered units and both groups of test units (p = 0.016). In biologic terms however, these differences were small. Red cells from an additional eight healthy volunteer donors were processed by an 8-hour room-temperature method and stored for 35 days. Studies in vivo 24-hour recovery of autologous red cells were performed by transfusing a radiolabeled (51Cr plus 131I-albumin) aliquot after 35 days' storage. Good recovery (mean > 80%) was found by both the single- and double-isotope-label methods. Recovery was significantly greater when calculated by the single-isotope method (p = 0.02). CONCLUSION : The combination of buffy coat removal and filtration in the blood container system with an integral filter achieved effective WBC reduction (> or = 3 log10 reduction from whole blood) without biologically significant detriment to in vitro or in vivo storage values.     

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.     

Improved preservation of coagulation factors after pre-storage leukocyte depletion of whole blood.

Plasma and red blood cell quality are affected both by citrate concentration and the levels of extracellular leukocyte and platelet derived substances, accumulated during storage of blood. The effect of leukocyte filtration on the storage stability of whole blood was therefore studied in blood collected in standard CPD and 0.5CPD (CPD with half strength citrate concentration). A total of 52 units, 12 of them with reduced citrate concentration, were leukocyte-filtered with Pall( whole blood filter (WBF1 or 3). No differences in leukocyte or platelet reduction were observed with the two citrate concentrations. However, with 0.5CPD a significantly longer filtration time and increased complement activation was observed. The effect of pre-storage leukocyte filtration on the plasma quality of whole blood was therefore only studied with standard CPDA1 anticoagulant solution (normal strength citrate concentration). Leukocyte filtration did not affect the von Willebrand factor concentration, while a small reduction (7%, p=0.04) in factor VIII (FVIII) concentration was observed. During storage, however, FVIII decreased more slowly in the filtered than in the unfiltered product, and, from day two, the FVIII content was significantly higher in the filtered product (46% versus 30% at 28 days, p<0.001). Factor V (FV) demonstrated a 16% reduction (p<0.001) upon filtration, followed by an additional 8% in the next 24 h and only a 4% reduction the next 27 days, while unfiltered products demonstrated a continuous reduction to 26% at 28 days. While the beta-thromboglobulin (beta-TG) concentration significantly increased (from 836 to 2483 IU/ml, p<0.001) during leukocyte filtration, no further increase was observed during storage. In contrast, unfiltered products demonstrated an increase to 5762 IU/ml (p<0.001) at 14 days, followed by a slight, not significant, reduction. This indicates platelet activation during filtration and explains a parallel reduction in FV. Filtration induced no increase in prothrombin fragment 1+2, while a slight increase was observed in some unfiltered products after 28 days of storage.Pre-storage leukocyte depletion thus improves the coagulation factor content of plasma in stored whole blood.     

Prion reduction of red blood cells: impact on component quality

BACKGROUND: A filter has been developed (P‐Capt, MacoPharma) to remove infectious prions from red blood cells (RBCs). We sought to assess 1) its operational use, 2) the quality of filtered components, and 3) whether filtration resulted in any significant changes to blood group antigens. STUDY DESIGN AND METHODS: A total of 272 leukoreduced RBC units, including units processed using “top‐and‐top” (TAT) and “bottom‐and‐top” (BAT) methods, were prion reduced using the P‐Capt filter. All RBCs were assessed using standard in vitro tests of RBC quality. Changes to blood group antigen expression were also investigated, including the exposure of cryptantigens and the ability of filtered RBCs to be crossmatched. RESULTS: Ninety‐nine percent of TAT units and 58% of BAT units had a hemoglobin (Hb) content of more than 40 g. Hemolysis increased immediately after filtration, but units remained within UK specification throughout storage. Prion reduction resulted in the loss of 7 to 8 g of Hb and reductions in hematocrit of 6% to 9% due to the filter containing 40 mL of saline, adenine, glucose, and mannitol. Other RBC quality data, including extracellular potassium, 2,3‐diphosphoglycerate, and adenosine triphosphate were similar to historical control data. There was no evidence of any immunologic changes of clinical relevance to the RBC membrane after filtration. CONCLUSIONS: Prion filtration does not appear to have a detrimental effect on basic in vitro measures of RBC quality or on blood group antigens as assessed by in vitro methods. However, prion filtration using the P‐Capt filter results in loss of Hb.