Prestorage Leukocyte Reduction with In-Line Filtration of Whole Blood: Evaluation of Red Cells and Plasma Storage

Objectives: Prestorage filtration of blood components appears to be an effective method to reduce leukocyte-induced adverse reactions and other complications. To determine whether it is better to filter whole blood before component separation, we compared the efficiency of in-line filtration of whole blood with that of postseparation filtration. Methods: Blood was collected from normal, healthy donors into either regular triple-bag containers or into whole-blood integral-filter container systems. We then compared the in vitro storage values of leukocyte-depleted red blood cell concentrates (RBCC) kept at 4 °C, and plasma frozen for 1 year with nonfiltered blood components as control. Results: All counts of white blood cells after filtration were < 1 × 10⁶ per unit. For almost all storage parameters no significant differences were found between leukocyte-reduced RBCC and control units. The plasma fibrinopeptide A values below 30 ng/ml prior to freezing indicate that filtration does not activate the coagulation factors. Furthermore, the filtration did not influence either the biological values or the coagulation factors of plasma units. Conclusions: Whole blood filtration prior to component preparation seems to offer a useful alternative technique for obtaining leukocyte-reduced RBCC and plasma.     

Leukocyte Depletion and Storage of Single-Donor Platelet Concentrates

Background and objectives: Because of widespread use of leukocyte reduction in platelet concentrates (PCs) and the need to store such concentrates, we investigated the effects of leukocyte depletion on the quality of stored PCs. Materials and methods: Ten double-sized PCs were divided into 2 equal units which were tested simultaneously. One half was stored for 5 days after filtration through a polyester filter, the other one was stored unfiltered. Results: The volume of the 10 ‘oversizeD' PCs was 483±40 ml (mean ± standard deviation) and they contained 5.9±1.5 × 10¹¹ platelets and 80±23 × 10⁶ leukocytes. Filtration significantly reduced the leukocyte concentration (168±56/μl before, 6±4/μl after filtration) and leukocyte count (39.9±11.3 × 10⁶ vs. 1.3±0.9 × 10⁶; p < 0.0005). Filtration caused a platelet loss of 16%, the platelet count decreasing not significantly from 2.91±0.75 × 10¹¹ to 2.40±0.94 × 10¹¹ (p = 0.26). After 5 days of storage all parameters of platelet function (platelet aggregation to several stimuli, hypotonic shock reaction [HSR] and platelet retraction), mean platelet volume, and pH and pCO₂ showed no advantage for PCs filtered prior to storage compared to PCs stored unfiltered. Moreover, platelet aggregation on day 5 using 4 agonists at 10 concentrations showed worse results in 4 assays in prestorage filtered PCs (collagen [4 μg/ml: p < 0.05, ADP [0.2 mM]: p < 0.05, ADP [0.3 mM]: p < 0.05, thrombin [0.6 E/ml]: p < 0.05). But there is no convincing trend in all aggregation tests, and HSR, presumably the most useful parameter, was not different on day 5. Conclusions: There is no advantage in terms of improved quality for prestorage leukodepletion of PCs. Taking into account the obvious disadvantages of filtration, such as platelet loss and increasing costs per transfusion, we conclude that pre- or post-storage filtration of single-donor PCs should be done only for patients who have a clear indication for the transfusion of leukocyte-poor blood products.     

Storage of Whole Blood for up to 24 Hours at Ambient Temperature prior to Component Preparation

The effect of rapid cooling to 20-24 degrees C of whole blood immediately after collection, using 'cooling units' with butane-1,4-diol and prolonged storage up to 24 h at ambient temperature was investigated in the whole blood and the subsequently prepared plasma, buffy coat and buffy-coat-poor red cell concentrate (BC-poor RCC) in saline-adenine-glucose-mannitol (SAG M) solution. Factor VIII:C content of the plasma (n = 10), after 24 h storage was 80 +/- 3% of the initial value. In routine procedures factor VIII:C content in the plasma (n = 129 pools of 20 donor units plasma) was 0.77 +/- 0.078 IU/ml, after storage of the whole blood for 16-20 h. In whole blood (n = 10), the 2,3-diphosphoglycerate (2,3-DPG) content of the red cells decreased from 4.36 +/- 0.55 to 1.47 +/- 0.6 mumol/ml red cells after 24 h storage at 20-24 degrees C. After storage of the BC-poor RCC (n = 10) at 2-6 degrees C for 1 week, the 2,3-DPG had dropped to 0.76 +/- 0.46 mumol/ml red cells. During the first 24 h of storage of whole blood, the adenine triphosphate (ATP) levels of the red cells remained stable. A mean increase of 20% of the initial value was observed after addition of SAG M solution. In the BC-poor RCC the ATP slowly decreased to 81 +/- 5% after 5 weeks and to 68 +/- 6.6% of the initial value after 6 weeks storage.(ABSTRACT TRUNCATED AT 250 WORDS)     

Differences in Residual White Blood Cell Subset Counts in Buffy Coat-Depleted Red Cell Concentrates Prepared with Bottom and Top or Quadruple-Bag Systems

Background: For preparation of buffy coat-depleted red cell concentrates (RCCs) in additive solution whole blood is currently collected in The Netherlands both in quadruple-bag and bottom and top bag systems. By using the quadruple-bag system both plasma and buffy coat cells are transferred into integrated satellite bags while the red cells remain in the collection bag. When bottom and top bags are used, the buffy coat remains in the collection bag while both red cells and plasma are transferred into satellite bags. The difference in processing prompted us to perform quantitative analysis of residual WBC subsets in buffy coat-depleted RCCs. Differences in removal of specific cells with the buffy coat could improve the outcome of additional filtration procedures aiming at complete removal of specific WBC subsets. Study Design and Methods: The buffy coat was removed in semiautomated procedures (Optipress I; Compomat G4) from units of whole blood collected in both bag systems. Paired samples were taken before and after removal of the buffy coat for counting and analyzing WBC subsets by flow cytometry using subset specific monoclonal antibodies. Results: All RCCs met the criteria from the guidelines of the Council of Europe. The percentage of residual total WBCs was lower (p < 0.001) in RCCs processed in bottom and top bag systems (26% Compomat and 18% Optipress) as compared to RCCs processed in quadruple-bag systems (43% compomat). WBC subset analysis in RCCs processed in quadruple-bag systems showed approximately 25% of residual T cells, B cells and monocytes and 60% of residual granulocytes. In contrast, WBC subset analysis in RCCs processed in bottom and top bag systems showed approximately 2% residual T cells, B cells, and monocytes and 35% residual granulocytes; in about 45% of units, lymphocytes and monocytes were even below the detection limit of flow cytometry analysis. Conclusion: Buffy coat-depleted RCCs are currently processed in bottom and top bag or quadruple-bag systems, the former being superior to the latter due to selective depletion of lymphocytes and monocytes by 98% (2 logs). The bottom and top procedure is an evident contribution to leukodepletion in blood transfusion, both with and without additional filtration.     

Influence of the Red Blood Cell Preparation Method on the Efficacy of a Leukocyte Reduction Filter

The performance of a leukocyte reduction bedside filter with different types of RBC concentrates was analyzed. Three types of RBCs were prepared: buffy-coat-depleted RBCs suspended in saline-adenine-glucose-mannitol (SAGM)-additive solution (BC-RBCs; n = 20), RBCs suspended in SAGM-additive solution without buffy coat removal (SAGM-RBCs; n = 20), and RBCs drawn in CPDA-1 conservative solution and processed for component preparation by the platelet-rich plasma method (CPDA-RBCs; n = 20). The units were filtered within 8 h of collection. One filter was used for every 2 units. High numbers of residual WBCs were found even in the units filtered first. Filtration of CPDA-RBCs resulted in a higher residual WBC content than SAGM-RBCs or BC-RBCs (p = 0.0032 and p = 0.0002, respectively). The filter performance strikingly decreased when the WBC load per filter exceeded 4 × 10⁹ or the platelet load was less than 100 × 10⁹. We conclude that filter performance varies with the WBC and platelet content of the RBC concentrates. Under the experimental conditions assayed in this study CPDA-RBCs are the least appropriate ones to be used for bedside leukocyte reduction.     

Preparation of Granulocyte-Poor Red Blood Cells by Microaggregate Filtration

Abstract. A simple, effective method for removing granulocytes from stored blood is described. Microaggregate filtration removes approximately 95% of the granulocytes from blood which has been stored for 2 weeks, centrifuged and filtered. The mean number of remaining leukocytes is 8 ± 3.7 × 10⁸/unit. The residual white cell population, which is composed almost entirely of lymphocytes, is substantially less than the average number of cells previously associated with febrile reactions. 45 patients were selected for the study. All had significant febrile transfusion reaction histories, and averaged one reaction for every 3.6 U of conventional red cell product transfused. Administration of 212 units of microaggregate filtered granulocyte poor red cells caused a 95% reduction in the incidence of fibrile reactions. The technique is inexpensive, easily incorporated into the routine of the clinical blood bank, and does not require 'open-system' processing. These considerations make microaggregate filtration a logical first choice method for the preparation of granulocyte-poor red blood cells.     

Passive Immunisation with IgG Endotoxin Core Antibody Hyperimmune Fresh Frozen Plasma

Postoperative complications have been associated with low pre-operative endotoxin core antibody (EndoCAb) status. Seventy-three patients scheduled to undergo elective cardiac surgery were screened for IgG EndoCAb levels 1 week prior to admission. Of these 73 patients, 39 had levels below the median of a healthy population (100 MU = median units/ml). Only 6 received an infusion of IgG EndoCAb hyperimmune fresh frozen plasma (FFP) due to surgical rescheduling or unavailability of compatible hyperimmune FFP. The 6 patients demonstrated significant elevation (p < 0.0001) of their IgG EndoCAb levels from a mean level of 43 MU/ml (range: 26–75) to a posttransfusion mean of 267 MU/ml (range: 227–300), which persisted until at least immediately prior to the operative period. We conclude that passive immunisation with EndoCAb hyperimmune FFP is possible prior to elective surgery and that the kinetic profile of such an administration will allow the FFP to be given the night prior to surgery and still maintain significantly elevated levels for surgery planned the following morning.     

Adsorption Filtration of Leukocyte-Reduced Single Donor Platelet Units

The effect of adsorption filtration of leukocyte-reduced single donor platelet (SDP) units collected on a CS-3000+ with a TNX chamber was compared to filtration of SDP units prepared via an isoradial chamber. The leukocyte enumeration technique employed a Nageotte chamber and had a nominal lower detection limit of 0.05 leukocytes/μl (if no cells were seen, the concentration was recorded as 0.01 μl). Although the prefiltration leukocyte content of the TNX units was unexpectedly low (2.4±2.8 times 10⁴ per unit), filtration reduced the leukocyte content further to no greater than 1.7±0.07 times 10³ (p<0.05). (The full extent of the leukocyte removal could not be assessed as no leukocytes were seen in counting any of the 20 filtered TNX units.) The 20 isoradial (control) SDP units achieved similar leukocyte depletion, with a postfiltration leukocyte content of 2.7±2.5 times 10³ (p>0.05, compared to filtered TNX units). Thus while significant leukocyte reduction occurred with adsorption filtration of both control and leukocyte-depleted SDP units, comparison of the relative degree of reduction awaits application of more sensitive leukocyte counting techniques. This study documented, however, that additional leukocyte reduction can be obtained by applying adsorption filtration to SDP units with an already low leukocyte content.     

Comparison of a Conventional Quadruple-Bag System with a ''Top-and-Bottom'' System for Blood Processing

'Top-and-bottom' bags have an outlet at the top and at the bottom of the collecting bag, allowing simultaneous expression of plasma and red cells, whereas the buffy coat remains in the collecting bag. The composition of blood components was investigated following manual separation of whole blood in a conventional 4-bag system (A) or automated separation in a 'top-and-bottom' system (B). To overcome inter-donor differences, two units of whole blood were pooled and redistributed into the original bags (A and B) prior to centrifugation. Leukocyte-poor platelet concentrates (LPPC) were manufactured from both types of buffy coat (A and B). The volumes of plasma, red cell concentrates (RCC) and buffy coat were similar in both methods. However, the residual leukocytes and platelets in the RCC from the top-and-bottom system were significantly lower than in the conventional system, 140 +/- 59 x 10(6) (mean +/- SD) versus 762 +/- 228 x 10(6), respectively (p less than 0.01). Both types of LPPC contained less than 10(7) leukocytes and could be stored for 7 days maintaining a pH above 6.5. We conclude that the top-and-bottom system enables automated and standardized preparation of RCC and plasma with a significantly better buffy-coat removal than with manual processing.     

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.     

Lipaemic plasma induces haemolysis in resuspended red cell concentrate

Introduction We investigated whether haemolysis in red cells suspended in plasma was affected by the lipid content and/or methylene blue (MB) treatment of fresh‐frozen plasma (FFP). We also investigated whether haemolysis was affected by the conditions under which lipaemic plasma was stored. Methods Study 1: Visibly lipaemic (n = 22) or nonlipaemic FFP (n = 24) units were thawed, pooled and split into identical pairs, one of which was MB treated. These units were used to resuspend red cell concentrates (RCC) and tested for haemolysis immediately and after 24 and 48 h of storage at 2–6°C. Study 2: Fresh plasma was aliquoted into 15‐ml tubes and stored in one of four ways as follows: room temperature; 2–6°C; frozen and thawed; or twice frozen and thawed. A sample of RCC was resuspended in each of these plasmas and haemolysis measured after 2 h. Study 3: Plasma was divided into 15‐ml tubes and stored as in study 2 followed by storage left standing upright in a refrigerator (2–6°C) for 24 h (with the exception of the room temperature sample). Plasma was separated into top, middle and bottom fractions and used to resuspend RCC that were assessed for haemolysis after 2 h. Results The levels of haemolysis in RCC were immediately greater when suspended in lipaemic plasma (0·70 ± 0·53% v 0·05 ± 0·06% for nonlipaemic plasma), which increased further on subsequent storage for 48 h (1·22 ± 0·40% v 0·15 ± 0·14% for nonlipaemic plasma). This was irrespective of whether plasma was MB treated. Lipaemic plasma stored frozen and then thawed resulted in the greatest haemolysis. In lipaemic plasma stored at 2–6°C, the chylomicron‐rich top fraction caused the highest level of haemolysis. Conclusion Haemolysis in red cells is increased in those suspended in lipaemic plasma and is dependent upon the storage conditions of that plasma prior to suspension. These data are relevant to the choice of plasma used to suspend red cells for neonatal exchange transfusion.     

Use of Segments for the Quality Control of the Factor VIII: Coagulant Activity of Fresh Frozen Plasma

The storage of fresh frozen plasma (FFP) for short periods at -20 degrees C for 6 weeks, -30 degrees C for 12 weeks, or -40 degrees C for 12 weeks, did not result in significant deterioration in factor VIII: coagulant (factor VIII:C) activity in the primary packs. In studies examining whether plasma segments could be used for quality control purposes, the mean factor VIII:C activity of the primary pack was found to be identical to that of the attached segments of plasma for units of FFP which were thawed within 2 h after preparation. This was also true for FFP units stored at -40 and -60 degrees C for up to 12 weeks. There was, however, a loss in factor VIII:C activity in the segments of FFP units stored at either -20 or -30 degrees C for 6 and 12 weeks, respectively. Thus for units of FFP stored at temperatures colder than -40 degrees C, segments are suitable for assessing the factor VIII:C activity in the primary pack but not for FFP units stored at -20 or -30 degrees C.     

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

SUMMARY. 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°. Median residual white cell content was 4 × 10⁵ when filtration was performed at 22° within 8 h of phlebotomy ( n = 20) and 3.2 × 10⁴ when filtration was performed at 4° 12-24 h after phlebotomy ( n = 24). None exceeded 1 × 10⁶ 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.     

Effect of rate and delay of cooling during initial cooling process: in vitro effect on red cells

Background Whole blood is stored at room temperature (RT) until processing into components. After separation and filtration, the RCC has to be cooled from RT to +2 – 6°C. Different start times of the cooling process and different cooling rates can be encountered in daily routine. The effect of these parameters of the initial cooling of leucoreduced red cell concentrates (LR‐RCC) on in vitro quality is not known. Methods In paired experiments (n = 12), LR‐RCCs in SAGM were cooled immediately after preparation from RT to +2 to +6°C either ‘fast’ (within 2½ h) or ‘slow’ (within 10–24 h) or ‘slow’ after a holding period of 6, 12, 18 or 24 h. Units were then stored at +2 – 6°C for 42 days and sampled at regular intervals for in vitro analysis. Results Irrespective of the start time and cooling rate during the initial cooling process, all units maintained good in vitro quality up to Day 42 with haemolysis <0·8%. Adenosine triphosphate (ATP) levels remained >2·7 μmol/g Hb in 99% of all units up to Day 35. Differences in pH, ATP content and 2,3‐DPG content between the groups were largest at Day 2 or 3 but generally disappeared during storage. Conclusion Start time and cooling rate of the initial cooling process had minor effects on in vitro quality of red cells. LR‐RCCs can be stored up to 24 h before cooling down to +2 – 6°C without deleterious effects on in vitro parameters during 42‐day storage.     

Prevention of Primary HLA Class I Allo-Immunization with Leucocyte-Poor Blood Components Produced without the Use of Platelet Filters

In a prospective study the incidence of allo-immunization and platelet refractoriness was investigated using a consequently leucocyte-poor blood product regime. Twenty-five previously non-transfused patients with acute leukaemia (11 men, 7 women) or autologous bone marrow transplantation for Hodgkin's or non-Hodgkin's lymphoma (2 men, 5 women) received at least 80 donor units of filtered red cells (filtration within 24 h after donation, leucocyte content 8.5 +/- 3.9 x 10(6)/U) and/or of platelet concentrate (produced by the buffy coat method, leucocyte content: 7.8 +/- 4.2 x 10(6)/U). A 1-hour recovery of 20% in three consecutive transfusions, in the absence of clinical factors known to impair increment, was defined as platelet refractoriness. HLA class I antibody screening with a panel of 60 cells was performed before the first transfusion and after 80 U of blood components. Of 25 patients who entered this study, 6 patients developed platelet refractoriness after a mean of 38 units of blood components (range 26-45 U); all 6 were female with a history of multiple pregnancies. In 19 patients regarded as non-refractory, no HLA antibodies were demonstrated (13 men, 6 women). This study, though limited in size, suggests that the use of blood products containing less than 1 x 10(7) leucocytes/donor unit prevents primary HLA class I immunization and platelet refractoriness.     

Large Volume Apheresis of Autologous Plasma and Preparation of Autologous Fibrin Glue from the Plasma

Abstract: Autologous blood transfusion (ABT) is useful for prevention of undesirable effects of allogeneic blood transfusion. In our hospital, not only autologous whole blood but also autologous red blood cells, autologous fresh frozen plasma (Auto‐FFP), and autologous fibrin glue (Auto‐FG) are routinely produced for surgical patients. The Auto‐FG is prepared from plasma which is separated from manually collected whole blood. However, when a large volume of Auto‐FG is required, the plasma obtained by an apheresis method may be useful. Therefore, a pilot study was conducted to determine whether a collection of 2 U (160 ml) of red blood cells (RBCs) and 400 ml of plasma at 1 apheresis is acceptable. We first performed the apheresis on healthy donors, and then applied for autologous blood donation. The apheresis is safe. The collected plasma is used for the production of Auto‐FFP and Auto‐FG. The remaining RBCs also are used for ABT. The preparation of Auto‐FG is simple, and it is effective for the reduction of allogeneic fibrin glue.     

Pooled Platelet Concentrates Prepared by the Platelet-Rich-Plasma Method and Filtered with Three Different Filters and Stored for 8 Days

Pooled platelet concentrates (PC) prepared by the platelet-rich plasma (PRP) method were filtered with three different filters and stored for 8 days at room temperature. The effect of filtration on leukocyte contamination, platelet concentration, and the in vitro function, morphology, metabolism and activation of platelets were studied. Eight pools of 20 PRP-PC were used, each pool was split into 4 equal volumes; 3 were filtered over a PL50HF, a PL-10A and a Bio P10 filter, the 4 served as a control. After filtration, leukocyte counts exceeded 3×10⁵ in none of the pooled PC. Platelet loss induced by filtration was about 17%. During storage, no differences in pH, PCO₂, and lactate and glucose concentration were found between the filtered and the unfiltered units, nor were any differences observed between filtered and unfiltered pooled PC in aggregation upon stimulation with collagen and/or ADP, adhesion capacity to collagen in flowing blood, nucleotide content of the platelets and nucleobase concentration in the plasma, expression of activation-dependent antigens, or platelet morphology as observed by light microscopy and by the swirling effect. Selective removal of β-thromboglobulin (22%) by the PL50HF filter was observed. Pooled PC prepared by the PRP-method can be filtered and stored for 8 days without detrimental effect on platelet function, metabolism or activation.     

Rotational Thromboelastometry or Conventional Coagulation Tests in Liver Transplantation: Comparing Blood Loss,Transfusions, and Cost

IntroductionOrthotopic liver transplantation (OLT) can be associated with significant bleeding requiring multiple blood product transfusions. Rotational thromboelastometry (ROTEM) is a point-of-care device that has been used to monitor coagulation during OLT. Whether it reduces blood loss/transfusions during OLT remains controversial.Materials and MethodsWe aim to compare ROTEM with conventional coagulation tests (aPTT, PT, INR, platelet count, fibrinogen) to guide transfusion of platelets, cryoprecip-itate, and fresh frozen plasma (FFP) during OLT over 3 years. Thirty-four patients who had transfusions guided by ROTEM were compared to 34 controls who received transfusions guided by conventional coagulation tests (CCT). Intraoperative blood loss, type/ amount of blood products transfused, and direct costs were compared between the two groups.ResultsThe ROTEM group had significantly less intra-operative blood loss (2.0 vs. 3.0 L, p = 0.04) and fresh frozen plasma (FFP) transfusion (4 units vs. 6.5 units, p = 0.015) compared to the CCT group (2.0L vs. 3.0L, p = 0.04). However, total number of patients transfused cryoprecipitate was increased in ROTEM (n = 25;73%) as compared to CCT (n = 19; 56%), p = 0.033. The direct cost of blood products plus testing was reduced in the ROTEM group ($113,142.89 vs. $127,814.77). Conclusion. In conclusion implementation of a ROTEM-guided transfusion algorithm resulted in a reduction in intra-operative blood loss, FFP transfusion and a decrease in direct cost during OLT. ROTEM is a useful and safe point of care device in OLT setting.     

Pall leukotrap affinity prion-reduction filter removes exogenous infectious prions and endogenous infectivity from red cell concentrates

BACKGROUND AND OBJECTIVES: Three recent probable cases of transmission of a variant of human Creutzfeldt-Jakob disease (vCJD) through blood transfusion suggest that the disease can be transmitted through transfusion of blood components from presymptomatic blood donors. In this study, we investigated the performance of a new filter for reducing the levels of infectious prions (PrP(Sc)) from red cell concentrates (RCC). MATERIALS AND METHODS: Endogenous Infectivity: A pool of 500 ml of whole blood was collected from 263K-strain scrapie-infected hamsters into an anticoagulant, processed into non-leucoreduced RCC (NL-RCC), and then passed through a prion-reduction filter. Pre- and postfiltration samples were tested for PrP(Sc) by Western blot and infectivity by inoculation of healthy hamsters. Results of the endogenous infectivity study after 200 days post-inoculation are discussed. Exogenous (Spiking) Study: Scrapie-infected hamster brain homogenates containing PrP(Sc) were added to human RCC and then filtered. Levels of PrP(Sc) were determined by Western blot assay. The effect of prior leucodepletion of 'spiked' RCC on PrP(Sc) removal by the prion-removal filter was also assessed. RESULTS: In the endogenous infectivity study, at 200-day observation time, the prefiltered RCC transmitted disease to six of the 187 hamsters, whereas the filtered RCC did not transmit disease to any of 413 animals, P = 0.001. The prion filter also significantly reduced the concentration of leucocytes in the RCC by about 4 logs, P < 0.05. In the exogenous (spiking) study, the level of PrP(res) was significantly reduced in RCC P < 0.05. Prior leucodepletion of the RCC with a leucoreduction filter did not significantly reduce the concentration of exogenously spiked PrP(Sc), P > 0.05. CONCLUSION: The use of this new prion-reduction filter should reduce the risk of vCJD transmission through transfusion of RCC, the most widely transfused blood component.     

Nine years of cascade filtration for thrombotic thrombocytopenic purpura

Thrombotic thrombocytopenic purpura (TTP) continues to attract physicians' attention because of its unpredictable course and underlying pathogenetic mechanisms. It is also attractive because of its optimal response to therapeutic plasma exchange (PE) even in the most severe cases. The usual approach to its treatment is conventional PE with plasma substitution and only recently fresh frozen plasma (FFP) has been substituted by cryodepleted or virally inactivated plasma with clinical results that are, if not better, at least comparable with the ones attained when FFP is employed. Nonetheless, no consensus exists regarding the optimal PE fluid and this is not of marginal interest as even after PE treatment mortality is still from 15 to 20%. On the contrary, some consensus exists on the pathogenetic relevance of the exceedingly large Von Willebrand (vWF) multimers whose presence parallels the clinical course and appears to be determined by the abnormalities in the production or function and survival of vWF-cleaving proteases which is auto-antibody mediated. In both cases plasmapheresis without plasma infusion is relatively ineffective, perhaps because it does not increase protease activity. Paradoxically, cascade filtration (CF) can produce the same favorable results without replacing any protease activity. As with CF, the replacement is the autologous plasma with approximately 20% levels of vWF, fibrinogen, fibronectin, IgM and circulating immune complexes and 75% of albumin, IgGs, AT III and proteins whose molecular weight exceeds 250-300000 Da. Our experience with CF for TTP began in 1994. Since then, 16 patients have undergone CF combined with decreasing amounts of FFP supplementation and since 1998 without any allogeneic FFP supplementation in 9 cases. Twenty-four patients (96%) treated with no or minimal amounts of FFP survived but four (16%) experienced from one to four recurrences associated with cutaneous, paradental, cholecystic and vaginal infections. Only one patient died (5%) after the second CF procedure. There were no untoward effects related to the procedure itself and up to 18 procedures in one patient were carried out over 16 months, 10 with the patient in her sixth month of pregnancy and four in the post partum period in preparation for a splenectomy. Remission was achieved after an average number of treatments (10.7 +/- 6.8); a result that compares favorably with those of our historical control group of 47 cases (14 +/- 13). The patient's exposure to allogenic plasma which was 10.8 +/- 4.6 plasma U/session was reduced to 0 in 10 patients, to 1.4 +/- 1.2 and 4.4 +/- 2.3 plasma U/session, respectively, for seven and nine patients receiving PE + CF and CF with same plasma supplementation as described in our previous article. Based on our experience, we believe CF is presently the optimal treatment for patients with classic, sporadic TTP.