A multicenter study on the efficiency of white cell reduction by filtration of red cells

To evaluate accurately the current performance of filtration, the French Produits Sanguins Labiles study group, composed of 21 transfusion teams, conducted a large-scale 6-month study involving over 1400 filtrations and 3000 controls. Some 745 standard red cell concentrates (RBC concentrates) and 690 concentrates previously white cell (WBC)-reduced by removal of buffy coat (BC-poor RBC concentrates) were filtered using six commercially available filters: at least 170 results were collected per filter, spread among a minimum of three teams. Prefiltration controls show that the removal (manual and automated) of the buffy coat results in an initial WBC reduction of approximately 63 percent, along with a hemoglobin loss of 4 g (7%). After filtration, residual WBCs were counted in the Nageotte manual counting chamber. The reliability of this counting method, which is simple and adapted to low WBC concentrations, was characterized in this study by a 25-percent coefficient of variation (CV) for a concentration of 2.5 WBCs per microL (i.e, 0.6 x 10(6) WBCs/filtered unit). The analysis of the results shows that, for five of six filters (1 filter was excluded), the postfiltration median value of residual WBCs was 1.1 x 10(6) in filtered RBC concentrates (n = 590), whereas it was 0.34 x 10(6) in filtered BC-poor RBC concentrates (n = 581). The difference is significant (p less than 10(-8), Wilcoxon test). Hemoglobin loss due to filtration varies according to the filter, from 5.7 +/- 2.2 to 17.3 +/- 2.5 g.(ABSTRACT TRUNCATED AT 250 WORDS)     

Mechanisms of white cell reduction in red cell concentrates by filtration: the effect of the cellular composition of the red cell concentrates

The effect of platelets on the removal of white cells (WBCs) from 16 to 24-hour-old red cell (RBC) concentrates by filtration was studied. RBC concentrates with various concentrations of platelets and WBCs were filtered on a cellulose acetate column filter and on three polyester flatbed filters. The microscopic study revealed that lymphocytes and most monocytes were captured in the smaller pores of the fiber network, irrespective of the brand of filter, the type of filter material, or the prefiltration platelet amount in the RBC concentrates. In contrast, efficient granulocyte depletion depended on granulocyte-platelet interaction and on the filter material. In the presence of platelets, granulocytes were captured in the top part of the column filter or in the coarse layers of two of the flatbed filters, where platelets covered the fibers. Platelet depletion of the RBC concentrates prior to filtration diminished the contribution of these parts of the filters to granulocyte capture. A larger part of the column filter or the fine layers of the flatbed filters were now required for granulocyte capture. In one of the flatbed filters, granulocyte-platelet interaction occurred mainly in the fine layers, which ended in blockage of this filter after the filtration of variable volumes (250-600 mL) of standard RBC concentrates. A quantitative estimation of the effect of platelets on the WBC-reduction capacity found that all three flatbed filters had a highly significant decrease (p = 0.001) in WBC-reduction capacity for platelet-depleted or buffy coat-depleted RBC concentrates, as compared with standard RBC concentrates.(ABSTRACT TRUNCATED AT 250 WORDS)     

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.     

Influence of temperature, filter wettability, and timing of filtration on the removal of WBCs from RBC concentrates

BACKGROUND: The efficacy of the removal of WBCs from buffy coat-reduced RBC concentrates by filtration is determined by many variables. The aim of this study was to investigate the influence of the filtration temperature, the wettability of the filter material, and the timing of the filtration after collection. STUDY DESIGN AND METHODS: The investigation used commercially available filters: 3 dry "online" filters (Cellselect FR, Fresenius Hemocare; BioR-01-max, Fresenius; Leucoflex LCG1, MacoPharma) and one wet "inline" filter (Leucoflex LCR4, MacoPharma) that contained saline-adenine-glucose-mannitol additive solution for RBCs and differed from the online version only in wettability. After buffy coat removal and suspension in saline-adenine-glucose-mannitol, filtrations were performed immediately at room temperature (RT) and after 2 hours' storage of the RBC concentrates at 4 degrees C, while the Leucoflex LCR4 was also tested after 24 hours' storage of the RBC concentrates at 4 degrees C. Sets of 12 pooled experiments were performed to prevent donor-dependent differences. RESULTS: The Cellselect FR gave significantly better WBC removal from RBC concentrates at 4 degrees C than at RT, with residual WBCs of 1.44 +/- 0.58 x 10(6) and 2.78 +/- 1.23 x 10(6), respectively (p<0.001). The BioR-01-max gave no significant difference: 0.62 +/- 0.27 x 10(6) WBCs (at 4 degrees C) versus 0.61 +/- 0.25 x 10(6) WBCs (at RT). Filtration with the Leucoflex LCG1 resulted in 0.06 +/- 0.03 x 10(6) and 0.07 +/- 0.07 x 10(6) WBCs at 4 degrees C and RT, respectively, which is not a significant difference. The Leucoflex LCR4, however, gave 2.08 +/- 0.84 x 10(6) WBCs at RT, 0.52 +/- 0.44 x 10(6) WBCs at 4 degrees C after 2 hours' cooling, and 0.05 +/- 0.10 x 10(6) WBCs at 4 degrees C after 24 hours' cooling (all p<0.001). CONCLUSION: Temperature, filter wettability, and timing of filtration after collection influence the efficacy of a filter for RBC concentrates. These variables need to be established, validated, and controlled before a filter can be selected for routine use.     

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.     

The mechanism of white cell reduction by synthetic fiber cell filters

The mechanism of white cell (WBC) retention by synthetic fiber-based WBC filters was studied. Filters were made of nonwoven fleece prepared from polyester, surface-modified polyester, or polypropylene fibers. Human platelet concentrates were filtered through experimental filters consisting of 8 to 54 layers of nonwoven fleece with mean pore sizes from 7.3 to 14.2 microns. Filters made of fleece of smaller pore size removed WBCs less effectively than filters with larger-pore fleece. Retention of lymphocytes and granulocytes gradually dropped to 0 percent as increasing loads were applied to the filters. The maximal retention capacity for these cell types (i.e., the number of cells retained when "saturating" numbers of WBCs were applied) was proportional to the number of layers of filter material used. Platelet retention did not correlate with WBC retention. Depth filtration, rather than mechanical sieving, seems to be the principal means of WBC removal by nonwoven fiber filters. A low initial number of WBCs in the component to be filtered is important for successful WBC filtration.     

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.     

Evaluation of HTLV-I removal by filtration of blood cell components in a routine setting

BACKGROUND: WBC depletion by filtration may prevent the transmission of HTLV-I, which requires cell-to-cell contact. The removal of HTLV-I-infected cells in routinely filtered blood cell components was measured. STUDY DESIGN AND METHODS: The study was conducted in Martinique where systematic screening for HTLV-I and -II and universal leukoreduction are mandatory. HTLV-I was quantified by use of real-time PCR in 8 RBC units and 4 PLT concentrates before and after filtration. HTLV-I proviral load in PBMNCs was determined in five of the eight HTLV-I-infected blood donors. RESULTS: The amount of MNC-associated HTLV-I DNA in RBC units before filtration was 21 x 10(6)+/- 29 x 10(6) copies (mean +/- SD). HTLV-I was detected in 4 of 8 RBC units after filtration, with a number of copies in the MNC fraction ranging from 20 to 140, following a 4.9 to 5.8 log reduction. Flow cytometry analysis performed in 2 of the filtered RBC units containing detectable HTLV-I showed suboptimal and out-of-range leukoreduction (0.56 x 10(6) and 1.22 x 10(6) residual WBCs). HTLV was not detected in filtered RBCs from the blood donor with the highest percentage of HTLV-I-infected PBMCs (9%). CONCLUSION: This study confirms that HTLV-I-infected cells can be detected in filtered blood cell components and shows that optimal leukoreduction is critical for HTLV-I removal.     

Effectiveness of two synthetic fiber filters for removing white cells from AS-1 red cells

Two commercially available synthetic fiber filters were studied for their effectiveness at removing white cells (WBCs) from AS-1-preserved red cells (RBCs) stored less than or equal to 14 days. In all, 65 filtrations were performed. An automated microprocessor-controlled hydraulic system designed for use with cellulose acetate fiber filters was employed to prepare filtered RBCs before release for transfusion. Studies were also carried out on polyester fiber filters, which are designed to be used in-line during transfusion. Residual WBCs were below the accurate counting range of Coulter counters and of conventional manual chamber counts. An isosmotic ammonium chloride RBC lysis method, plus a modified chamber counting technique, permitted a 270-fold increase over the number of WBCs counted by the conventional manual method. For the polyester fiber-filtered products, residual WBCs per unit were not affected by speed of filtration, prior length of storage, or mechanical tapping during filtration. The effectiveness of WBC removal (mean 99.7%), total residual WBCs (means, 4.8 and 5.5 x 10(6], and RBC recovery (mean, 93%) was the same for both filters. The majority of residual WBCs were lymphocytes. WBC removal and RBC recovery were strikingly superior to results reported with nonfiltration methods.     

Quality control of red cell filtration at the patient's bedside

BACKGROUND: Concern has been raised about the quality of white cell (WBC) reduction in blood components when it is performed by filtration at the patient's bedside. Thus, the quality of red cell (RBC) filtration performed at the bedside through two new flatbed WBC- reduction filters was evaluated. STUDY DESIGN AND METHODS: In the laboratory, 25 and 10 RBC units suspended in additive solution were stored for 1 to 2 and 14 to 21 days, respectively, and filtered through each filter. At the end of filtration, an automated complete blood count and a manual WBC count (Nageotte chamber) were determined in two samples collected from 1) a segment clamped at 5 and 25 cm below the filter along the line connecting prefiltration and postfiltration bags and 2) the postfiltration bag. In addition, 10 of the 11 nurses of the hematology outpatient clinic administered to hematologic patients 25 RBC units stored for 1 to 2 days through each type of filter. At the end of transfusion, a segment was collected from the transfusion set and a WBC count was performed as described above. No filter priming or rinsing with saline was done. RESULTS: WBC counts obtained after laboratory filtration in the segments were similar to those obtained from the postfiltration bags and from the segments collected at the bedside in all cases, with the exception of 14- to 21-day-old RBCs filtered in the laboratory through one of the filters, which produced slightly higher WBC counts in the segments than were seen in the postfiltration bags. The difference was not significant. In no case was the count in the postfiltration bag higher than that in the segment. Nurse training was easy, and bedside filtration was associated with no untoward effects. CONCLUSION: The RBC filtration at the patient's bedside can be equal in quality to that performed in the laboratory, at least in such clinical settings as hematology and oncology departments in which blood transfusion is common practice, and if simple training is provided to the nursing staff. Under the conditions of this study, it seems that quality control of RBC bedside filtration is feasible and simple.     

Research and development in the blood bank: Efforts of a hospital donor center to improve efficiency of in-line leukocyte reduction filters for automated plateletpheresis

In-line leukocyte reduction filters (LRF) are available for use with an automated plateletpheresis (PPH) system. Initially, 62% of PPH units produced with such a filter (LRF6, N = 29) had postfiltration (POF) white blood cell (WBC) counts <5 × 10⁶, with a mean POF WBC of 42 × 10⁶. In an attempt to decrease POF WBCs, PPH were rested 30 to 60 minutes before filtration with LRF6. A new, larger-volume LRF (LRF10) was also assessed for its efficiency of leukodepletion. A total of 625 PPH, 490 filtered with LRF6 and 135 with LRF10, were evaluated using prefiltration (PRF) and POF samples. Mean prefiltration WBC loads averaged 80 × 10⁶ (range, 60–88 × 10⁶) using seven combinations of filters, collection software, and PRF rest periods. Ninety-three percent of PPH units rested prior to filtration with LRF6 (N = 237) had <5 × 10⁶ WBC POF, with a mean of 5 × 10⁶ WBC POF. All PPH units filtered with LRF10 (N = 135), whether rested or not, had <5 × 10⁶ WBC POF, with a mean WBC count of 0.2 × 10⁶ POF. Mean platelet (PLT) yields POF ranged from 3.1 to 3.4 × 10¹¹. A PRF rest decreased mean POF WBC counts in products filtered with LRF6. The LRF10 consistently produced PPH with <5 × 10⁶ WBC POF. Blood centers must thoroughly validate equipment utilized in the production of blood components.     

WBC reduction in cryopreserved RBC units

BACKGROUND: WBC reduction of blood components by filtration is widely practiced to decrease the incidence of alloimmunization. Freezing RBCs reduces the WBC load but is insufficient to achieve the currently recommended US limit of 5 x 10(6) cells per unit. STUDY DESIGN AND METHODS: Blood units were WBC reduced by filtration or by buffy-coat (BC) removal and then frozen in the presence of a high-glycerol concentration. The count of residual WBCs was determined by flow cytometry after deglycerolization. RESULTS: Without WBC reduction, the total number of WBCs present after freezing and thawing was 11.5 +/- 9.2 x 10(6) WBCs per unit (n = 18). Particulate residues from monocytes and neutrophils that were detected in the remaining cell populations were positive for CD66b, CD3, CD14, and CD41. Removal of 40 mL of BC at the time of blood collection lowered the number of WBCs after freezing and deglycerolization to 1.9 +/- 1.20 x 10(6) per unit (n = 11). Similar results were obtained when only 20 mL of BC was removed using a modified blood-bag design. Unfiltered RBC units that were stored for 15 days at 4 degrees C after BC removal contained fewer than 5 x 10(6) WBCs after deglycerolization. Units WBC reduced by filtration before freezing had no detectable WBCs after thawing and washing (n = 14) and did not contain particulate residues. Filtration after deglycerolization was effective in reducing the WBC count below 10(6), although some debris was still present. CONCLUSION: RBC freezing alone will not reduce residual counts to recommended levels. However, initial removal of BC can provide an economical alternative to WBC filtration for cryopreserved units. Units that were not WBC reduced before freezing can be filtered after deglycerolization when needed.     

WBC content of platelet concentrates prepared by the buffy coat method using different processing procedures and storage solutions

BACKGROUND: The number of WBCs in platelet concentrates (PCs) prepared by the buffy coat (BC) method with different storage solutions can result in low (5 x 10(6)/unit) WBC levels by the use of careful centrifugation techniques without filtration. At present, most blood banks use filtration steps to meet these requirements. The difference in processing methods and suspension solutions prompted the investigation of the influence of the various procedures on the WBC and platelet content of PCs. STUDY DESIGN AND METHODS: PCs from 5 BCs were harvested without or with inline filtration (AutoStop BC, Pall Corp.) in either plasma (PCs-plasma) or platelet additive solution (PCs-PAS-2). After preparation, samples were taken for counting WBCs and platelets and for analyzing WBC subsets by flow cytometry using specific MoAbs. The WBCs were concentrated before analysis of the WBC subsets. Results less than 2.5 cells per microL were considered below the limit of accuracy of the subset analysis. RESULTS: All filtered PCs met the AABB standard of 5 x 10(6) per unit and the European guidelines of 1 x 10(6) per unit. None of the nonfiltered PCs met the European guidelines, but all met the AABB guidelines. All filtered units gave residual WBC counts below the detection limit for subset analysis. Filtered PCs-plasma gave significantly higher platelet counts than filtered PCs-PAS-2 or nonfiltered PCs (p<0.01, ANOVA). CONCLUSION: Careful centrifugation of pooled BCs, with plasma or PAS-2, can result in PCs with low WBC contamination levels. However, filtered PCs are superior, because of better WBC removal and higher platelet counts.     

White cell reduction in platelet concentrates and packed red cells by filtration: a multicenter clinical trial. The Trap Study Group

BACKGROUND: Most previous studies on white cell (WBC) reduction by filtration have been small-scale studies conducted under tightly controlled laboratory conditions. Their results would be the ideal, rather than what might be expected during routine operation. STUDY DESIGN AND METHODS: To obtain information on routine filtration of blood components, data have been collected from a large-scale, ongoing, multicenter clinical trial designed to determine the effectiveness of WBC reduction in or ultraviolet B radiation of platelet concentrates before transfusion in preventing platelet alloimmunization and platelet transfusion refractoriness. The WBC content of blood components both before and after filtration was determined by automated cell counters and a manual propidium iodide-staining method, respectively. Platelet and red cell losses during filtration were measured. RESULTS: The average platelet losses after filtration were 24 +/? 15 percent and 20 +/? 9 percent for apheresis platelets and pooled platelets, respectively. The frequencies at which filtered platelet concentrates contained high levels of residual WBCs (> 5 × 10(6)) were 7 percent and 5 percent for apheresis platelets and pooled platelets, respectively. Further analysis of the platelet filtration data showed that greater numbers of total initial WBCs in the pooled platelets were associated with increased percentages of filtration failure (> 5 × 10(6) residual WBCs). For packed red cells, the average losses during filtration were 23 +/? 4 percent and 15 +/? 3 percent for CPDA-1 units and Adsol units, respectively. The frequencies at which filtered red cells contained > 5 × 10(6) residual WBCs were 2.7 percent for one type of filter and 0.3 percent for another type of filter. CONCLUSION: There were significant losses of platelets during filtration, which could add to the costs of WBC reduction and lead to possible increases in donor exposures. Filtration failures still occurred, despite careful observation of the standard filtration procedures. The number of total WBCs in pooled platelets before filtration has been identified as an important factor in determining the success of WBC reduction.     

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.     

Depletion of white cells from platelet concentrates with a new adsorption filter

Removal of white cells (WBCs) from platelets may reduce alloimmunization to WBC antigens, prevent febrile reactions, and improve platelet increments in multiply transfused patients receiving HLA-matched platelets. A new surface-modified fibrous polyester filter was evaluated; it requires no special processing of pooled platelet concentrates and can be used at the patient's bedside. The studies were designed to measure WBC removal, platelet function, in vitro platelet recovery, and in vivo platelet survival. WBC mean removal was 99.8 percent +/- 0.56 (n = 37) when a pool similar in volume to 6 platelet concentrates was tested. The mean number of residual WBCs after filtration was 5.6 x 10(5). In vitro mean platelet recovery was 86.9 percent for a pool size of 6 units (n = 37). Clot retraction and platelet aggregation were unaffected by filtration. Survival studies of 111Indium-labeled platelets done with filtered autologous platelets showed no reduction in the normally expected survival. These studies indicated that the filter efficiently removes WBCs without substantially decreasing platelet number, survival, or function. This device offers the potential of considerably improving platelet transfusion therapy.     

Biocompatibility of white cell filters as evaluated by complement activation

The biocompatibility of nine different white cell filters was examined by analysis of complement activation in plasma specimens obtained from blood components before and after filtration. Filters for both red cell (RBC) concentrates and platelet concentrates (PCs) were tested. It was found in all of the filters tested that the postfiltration levels of complement activation products were not higher than the prefiltration levels in RBC concentrates and PCs. One exception was the filtration of multiple PCs with Imugard IG-500, in which case a rise in C3 activation products was seen. Moreover, there was a significant rise in C3 activation products, but not the terminal complement complex, when plasma was filtered through Imugard E, which contrasted with results with the other filters. High initial and storage time-dependent levels, especially of C3 activation products, were observed in the PCs, probably due to their processing at room temperature. It can be concluded that the majority of the filters tested do not activate complement.     

WBC subset analysis of WBC-reduced platelet components

BACKGROUND: WBC-reduced platelet components may be prepared by filtration or apheresis processing. Both methods have previously been shown to result in a residual total WBC content <5 x 10(6) per component. However, there may be differences in the efficacy of these techniques for removing certain WBC subsets. STUDY DESIGN AND METHODS: Two multiparameter flow cytometric assays were developed and validated to perform WBC analysis on WBC-reduced platelets collected with two apheresis instruments (Amicus and COBE Spectra) and on 6 units of filtered pooled random-donor platelet concentrates. RESULTS: All components contained <1 x 10(5) WBCs. The COBE Spectra and Amicus apheresis platelet components contained more WBCs than did filtered pooled platelets (p<0.05). Lymphocytes (T and B), monocytes, and granulocytes were identified in all components. Granulocyte content was lowest in the Amicus components and filtered pools. Monocytes were lowest in filtered pools. Amicus platelet components had fewer granulocytes and monocytes than the COBE Spectra platelets. Amicus and COBE Spectra components contained more lymphocytes than the filtered pools. CONCLUSION: Multiparameter flow cytometry can be used to quantify and characterize WBCs in WBC-reduced platelet components. WBC reduction by filtration or apheresis was highly effective. WBCs from each subset were identified in all components. Although filtered pools had the lowest numbers of WBCs, the very low numbers observed in all components suggests that the absolute quantitative differences in WBC subset content are of questionable clinical significance.     

Quality control of white cell-reduced red cells: white cell preservation and simplified counting

BACKGROUND: White cell (WBC) degradation restricts the interval between the filtration process and the assay for residual WBCs. Maintaining WBC integrity would permit extended sample storage for batching and/or shipment to centralized laboratories. The usual quality control assay for WBC-reduced red cell units requires determining the number of WBCs in the entire counting area of a Nageotte hemocytometer, which consists of 40 rows. Reducing the counting area would simplify the quality control procedure. STUDY DESIGN AND METHODS: Adsol red cell units were prepared either on the day of collection (Day 0) or on Day 1 and WBC reduced by filtration on the same day. By using prefiltration and postfiltration red cells, samples containing WBC concentrations of 15, 10, and 3 WBCs per microL were prepared by serial dilution. Identical samples were treated with glutaraldehyde and stored at either 20 to 24 degrees C or 1 to 6 degrees C. All samples were assayed on the day of component preparation and on Days 7 and 14. The numbers of WBCs corresponding to 10- and 40-row areas of the Nageotte hemocytometer were determined. RESULTS: For the conditions and WBC concentration range studied, no significant changes in WBC concentrations were observed through Day 14 for glutaraldehyde-treated samples stored at either temperature, although there were substantial decreases in untreated samples. A 10-row measurement was determined to be sufficient for identifying WBC-reduced red cell units passing the present limit of 5 × 10(6) residual WBCs. CONCLUSION: Glutaraldehyde treatment can preserve WBCs in red cell samples at least up to Day 14, which provides increased efficiency in quality control for laboratories. Current red cell WBC-reduction filters produce components that, when assayed, contain fewer than 10 WBCs per full counting area. The simplified procedure would allow reduction of the counting area by 75 percent.     

WBC reduction in RBC concentrates by prestorage filtration: multicenter experience

BACKGROUND: As universal leukocyte (WBC) reduction (ULR) is being considered as a new standard, few data are available on the performance of WBC-reduction filtration in routine practice. The performance of WBC-reduction in RBCs, using varied filtration practices, in meeting the current FDA requirement (<5 x 10(6)), Council of Europe (EC) recommendation, the proposed FDA requirement (<1 x 10(6)), and a more stringent proposal (<5 x 10(5)) for residual WBCs per RBC unit was assessed and compared. STUDY DESIGN AND METHODS: Participating facilities were the 11 sites of the Viral Activation Transfusion Study (VATS), a prospective study of the impact of transfusion with and without WBC-reduction on survival and HIV viral load in HIV-1-infected patients. Patients randomly assigned to undergo WBC reduction were required to receive RBCs < or =14 days old that had undergone prestorage (within 72 hours of collection) WBC-reduction filtration by a method devised to achieve a postfiltration WBC count of <5 x 10(6). Residual WBC quantitation was performed by PCR in the central VATS laboratory by using frozen WBC-reduced RBC samples obtained at issue for transfusion. RESULTS: A total of 1869 WBC-reduced RBC units were studied. Filtration practices varied within and between sites. There were significant differences in mean residual WBC counts at the 11 sites (p<0.001). Among the WBC-reduced RBC units, 0.8 percent exceeded 5 x 10(6) WBCs per unit, 8.3 percent exceeded 1 x 10(6) WBCs per unit, and 14.3 percent exceeded 5 x 10(5) WBCs per unit. CONCLUSION: Residual WBCs in WBC-reduced RBC units vary within and between sites. WBC reduction was successful, in that over 99 percent and 91 percent of VATS WBC-reduced RBC units met US and EC thresholds, respectively. However, the small but measurable failure rate indicates that not every unit will meet these guidelines.