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PubMed2005

Robust scale-up of dead end filtration: impact of filter fouling mechanisms and flow distribution.

Robust design of a dead end filtration step and the resulting performance at manufacturing scale relies on laboratory data collected with small filter units. During process development it is important to characterize and understand the filter fouling mechanisms of the process streams so that an accurate assessment can be made of the filter area required at manufacturing scale. Successful scale-up also requires integration of the lab-scale filtration data with an understanding of flow characteristics in the full-scale filtration equipment. A case study is presented on the development and scale-up of a depth filtration step used in a 2nd generation polysaccharide vaccine manufacturing process. The effect of operating parameters on filter performance was experimentally characterized for a diverse set of process streams. Filter capacity was significantly reduced when operating at low fluxes, caused by both low filtration pressure and high stream viscosity. The effect of flux on filter capacity could be explained for a variety of diverse streams by a single mechanistic model of filter fouling. To complement the laboratory filtration data, the fluid flow and distribution characteristics in manufacturing-scale filtration equipment were carefully evaluated. This analysis identified the need for additional scale-up factors to account for non-uniform filter area usage in large-scale filter housings. This understanding proved critical to the final equipment design and depth filtration step definition, resulting in robust process performance at manufacturing scale.

Biological Products↗

PubMed1994

Immunologic significance of a collagen-derived culture filtrate containing proteolytic activity in Aspergillus-related diseases.

BACKGROUND: Despite increasing evidence implicating fungal proteases in the virulence of pulmonary fungal diseases, routine fungal culture media do not favor protease production. Hence, filtrates that serve as the source of antigen for serologic determinations are poor in proteases, and consequently, the immunologic significance of these enzymes is unknown. METHODS: A clinical isolate of Aspergillus fumigatus was cultured on collagen medium, resulting in excretion of high levels of fungal proteases in the culture filtrate. This was compared with standard culture filtrates by diverse analytic techniques including immunoblotting with sera of patients with pulmonary aspergilloma (PA) and allergic bronchopulmonary aspergillosis (ABPA). RESULTS: Protein profiles of collagen medium filtrate showed several (glyco)proteins not found in conventional culture filtrates, including a prominent 32 kd glycoprotein, which coisolated in gel filtration and ion-exchange chromatography with elastase activity, as well as 67 kd and 94 kd (glyco)proteins. Intense IgG binding was seen with the 32 kd glycoprotein when ABPA and PA sera were used. The 94 kd protein showed intense binding with PA sera but not with ABPA sera, whereas for the 67 kd glycoprotein the reverse tended to be the case. CONCLUSION: Fungal culture on collagen media results in the production of filtrates with high protease activity, containing unique (glyco)proteins of which at least one (32 kd) is closely associated with fungal elastase activity. These constituents are immunologically relevant, eliciting IgG production in patients with PA and ABPA, suggesting production of these (glyco)proteins during disease in vivo. The use of collagen media filtrates may enhance our serodiagnostic capacity in patients with fungal pulmonary diseases.

Aspergillosis↗

PubMed2000

Nonpenetrating filtration surgery for glaucoma: control by surgery only.

PURPOSE: To report on intraocular pressure (IOP) control by nonpenetrating filtration surgery without medical treatment in eyes with primary open-angle glaucoma (POAG). SETTING: Oxford Eye Center and St. John Eye Hospital, Johannesburg, South Africa. METHODS: This retrospective study evaluated IOP control by nonpenetrating filtration surgery in 46 patients (86 eyes) with POAG who had surgery between February 1992 and February 1998 (mean follow-up 46 months); 48 eyes were previously treated, and 38 were newly diagnosed, untreated eyes. Under a trapezoidal scleral flap, a deep sclerectomy and a fenestration in Schlemm's canal were created without penetrating the anterior chamber. Postoperatively, when IOP rose above 20 mm Hg, instead of adding medical treatment, the filtration site was revised to re-establish filtration. RESULTS: The mean drop in IOP was 50%, from a mean of 30.4 mm Hg preoperatively to a mean of 15.35 mm Hg postoperatively. After a mean period of successful filtration of 29.9 months, the filtration site was revised in 48 eyes (56%) to maintain the IOP below 21 mm Hg without medication. The reoperation rate was 4.7 times higher in previously treated patients than in untreated patients. CONCLUSIONS: Nonpenetrating filtration surgery in eyes with POAG was more rewarding in untreated patients than in medically treated patients. To control IOP without medication, revision of the filtration site is feasible and needed in the medium and long term.

Adult↗

PubMed1994

The rice culture filtrate of Bacillus cereus isolated from emetic-type food poisoning causes mitochondrial swelling in a HEp-2 cell.

Rice culture filtrates of Bacillus cereus SA-50, an emetic-type strain, produced a toxin which caused cytoplasmic vacuole formation in HEp-2 and HeLa cells. Electron microscopic observation revealed that the apparent vacuoles in HEp-2 seen under a light microscope were actually swollen mitochondria. The oxygen consumption of HEp-2 cells was accelerated by the addition of the rice culture filtrate as was measured with a polarographic oxymeter; a respiratory control ratio was 1.0 for control cells, while 1.4 for ones with the filtrates. The culture filtrates showed a similar effect on the isolated mouse liver mitochondria; respiratory control ratios for the mitochondria with and without the filtrates were 3.6 and 1.0, respectively. The affecting manner of the culture filtrates on the oxygen consumption of mitochondria was similar to that of 2,4-dinitrophenol, suggesting that the culture filtrate contains a toxin acting as an uncoupler of oxidative phosphorylation in mitochondria. It is likely that the culture filtrates containing the emetic toxin of B. cereus causes mitochondrial swelling with a close relationship to the uncoupling of the oxidative phosphorylation of mitochondria.

Animals↗

PubMed1964

RESISTANCE-ENHANCING ACTIVITY OF CULTURE FILTRATES OF MYCOBACTERIUM TUBERCULOSIS.

Hedgecock, Loyd W. (Veterans Administration Hsopital, St. Louis, Mo.). Resistance-enhancing activity of culture filtrates of Mycobacterium tuberculosis. J. Bacteriol. 88:1349-1355. 1964.-It was demonstrated that filtrates of cultures of Mycobacterium tuberculosis exhibit resistance-enhancing activity against infection with Klebsiella pneumoniae and Diplococcus pneumoniae. Resistance was demonstrable when the culture filtrate was injected 3 hr prior to challenge with K. pneumoniae, and reached the highest level when injected 24 hr before challenge. Protection was maximal when the filtrate and challenging organisms were injected by the same route. After infection with K. pneumoniae, the bacterial titers in the tissues of filtrate-treated animals were significantly lower than those of untreated susceptible controls. Mice injected with the filtrate 24 hr previously demonstrated significantly increased rates of clearance of injected carbon from the blood. In examination of a variety of mycobacteria, resistance-enhancing activity was found only in culture-filtrates of pathogenic mycobacteria, the highest concentration occurring in filtrates of virulent organisms. The injection of a relatively large amount of phenol-killed cells of all of the mycobacteria examined enhanced resistance to infection with K. pneumoniae.

Animals↗

PubMed2005

Chest radiography with a flat-panel detector: image quality with dose reduction after copper filtration.

PURPOSE: To compare image quality and estimated dose for chest radiographs obtained by using a cesium iodide-amorphous silicon flat-panel detector at fixed tube voltage and detector entrance dose with and without additional 0.3-mm copper filtration. MATERIALS AND METHODS: The study was approved by the institutional ethics committee. All prospectively enrolled patients signed the written consent form. Chest radiographs in two projections were acquired at 125-kVp tube voltage and 2.5-microGy detector entrance dose. The experimental group (38 patients) was imaged with 0.3-mm copper filtration; the control group (38 patients) was imaged without copper filtration. An additional 12 patients were imaged with and without copper filtration and served as paired subject-controls. Three readers blinded to group and clinical data independently evaluated the radiographs for image quality on a digital display system. Twelve variables (six for each radiographic projection) were assigned scores on a seven-point ordinal scale. Scores between experimental and control groups were compared: Logistic regression analysis and Mann-Whitney U test were used for unpaired patients; and Wilcoxon and McNemar test, for paired patients. In all, 72 comparisons were determined (36 [12 variables x three readers] for unpaired patients and 36 for paired patients). In a phantom study, radiation burden of experimental protocol was compared with that of control protocol by using Monte Carlo calculations. RESULTS: For 70 of 72 comparisons, digital radiographs obtained with copper filtration were of similar image quality as radiographs obtained without copper filtration (P = .123 to P > .99). For two of 72 comparisons, one observer judged the experimental protocol superior to the control protocol (P = .043, P = .046). Patient dose reduction estimated with Monte Carlo calculations was 31%. Use of copper filtration increased exposure times by 48% for posteroanterior views and by 34% for lateral views. CONCLUSION: Subjectively equivalent chest radiographic image quality was found with estimated 30% dose reduction after addition of 0.3-mm copper filtration with flat-panel cesium iodide-amorphous silicon technology.

Cesium↗

PubMed1996

Simultaneous estimation of filtration variables in isolated rat lungs in zone 3 conditions.

Estimation of filtration variables (filtration coefficient, perimicrovascular pressure, and reflection coefficient) is important for evaluating pulmonary microvascular permeability to fluids, especially when the lungs are inflamed, injured, or being preserved for transplantation. Here we report a new method for estimating filtration variables simultaneously in isolated rat lung lobes in zone 3 conditions (pulmonary arterial pressure > pulmonary venous pressure > alveolar pressure). We used Krebs-Henseleit solution containing 6% bovine serum albumin for the perfusate and maintained perfusion using a constant-pressure circuit system. Pulmonary venous and alveolar pressures were kept at 2.5 and 2.0 cmH2O, respectively, and pulmonary arterial pressure was set so that lung weight did not change. Then we increased both pulmonary arterial and venous pressures by 3 cm H2O simultaneously, and recorded the weight gain. Next, we diluted the perfusate with Krebs-Henseleit solution to about half the original concentration, and recorded the weight gain. Using the Starling equation, the values we obtained for the filtration variables were filtration coefficient, 5.3 mg. min-1.cmH2O-1.g-1; perimicrovascular pressure, 1.1 cmH2O; reflection coefficient, 0.54. These values agree with values from previous reports. Since these 3 filtration variables are interrelated, this method for simultaneous measurement is more accurate than independent measurements are. The advantages of this method are that it does not require direct measurement of interstitial pressure or collection of lymph fluid. What we need to calculate these filtration variables are the initial filtration rates and the albumin osmotic pressures for perfusate.

Animals↗

PubMed1976

Differentiation of lymphoid cells: the non-mitogenic induction of immunoglobulin production by thymus cell extract and thymus cell culture filtrate.

The cell-free medium in which thymocytes have been cultured (filtrate) as well as sonic lysates of thymocytes (extract) enhance immunoglobulin production when added to spleen cells during tissue culture. In spite of the requirement for foetal calf serum in the culture medium, production of the enhancing factor in thymocyte culture filtrates occurred even in the presence of a variety of metabolic inhibitors including NaN3, puromycin and hydroxyurea. Although DNA synthesis is required as a prelude to the induction of immunoglobulin production, two lines of evidence indicate that the enhancement produced in response to filtrate and extract occurs via a non-mitogenic process. First, neither cell-free agent was mitogenic toward spleen cells. Secondly, the enhancement of immunoglobulin production due to filtrate or extract was observed even in the presence of inhibitors of DNA synthesis. Multiple functions for thymocytes in the induction of immunoglobulin production are indicated by the findings that thymocytes restore immunoglobulin production of anti-thymocyte serum-treated spleen cells, whereas filtrate and extract, alone or in combination, do not have this capability. Furthermore, filtrate and extract failed to enhance the induction of DNP-group-specific antibody production by cells incubated with DNP-protein, but filtrate and extract could partially restore anti-DNP antibody production of such anti-thymocyte serum-treated cells. The role of thymocytes, filtrate and extract in the antigen-independent and the antigen-dependent induction of immunoglobulin production is discussed.

Animals↗

PubMed1981

Study on relationship between erythrocyte filtration and other risk factors in diabetic angiopathy.

Red blood cell filtration test has been performed in 37 insulin dependent diabetics (IDD) and 35 controls matched for age and sex and subdivided into age groups. IDD have been classified according to the presence of vascular complications, either affecting small and/or large vessels, assessed by clinical and instrumental methods. Results evidence a close correlation between age, fibrinogen, smoking and filtration index, both in IDD and in controls. The presence and type of vascular complication in diabetics parallels the increase in the filtration index, being the blood of macroangiopathic diabetics less filtrable than that of non angiopathics and/or controls. Metabolic control, recorded as glycosylated haemoglobin shows a slight correlation with filtration index, while blood glucose of the same specimen does not. Filtration index appears to be an useful datum for assessing angiopathic risk in diabetics. Nineteen IDD have been treated with pentoxifylline, 400 mg per os 3 times daily for 20 days and filtration time, and other metabolic variables have been assessed. Data evidenced a marked improvement in the filtration time without any change in the other metabolic variables suggesting that the effect of this drug is mainly exerted on the RBC deformability and not on plasma viscosity. The drug has been very well tolerated and revealed itself an effective therapeutic mean for influencing RBC filtration, thus preventing angiopathic phenomena.

Diabetes Mellitus, Type 1↗

PubMed1995

The effects of filtration on protein nucleation in different growth media.

Filtration effects of turkey egg white lysozyme solution (TEWL) prior to subjecting it to crystallization conditions are investigated. Filtering TEWL solution and crystallizing it in ungelled media significantly decreased the number of conditions yielding crystals. This decrease dependent on the membrane cut-off used for filtration. From this, the postulated factors aiding in nucleation are estimated to be 0.17 microns in diameter. The existence of these factors was verified by the procedure of reversed filtration: filtered solutions passed through their inverted filter membrane a second time lead to improved crystallization results. The effect of aging of the TEWL solution prior to subjecting it to ungelled crystallization conditions was also verified. We did not find any time-dependent change in the size or the number of crystals per drop. Repeating the filtration experiments in agarose-gelled crystallization media showed that the influence of filtration on the crystallization outcome was significantly diminished. Far better crystallization results were obtained compared to ungelled media. However, there is a certain aging effect linked to filtration in gelled media. Different crystallization results were obtained depending on whether filtration was performed before or after aging and subsequent crystallization. This suggests a secondary time-dependent effect.

Animals↗

PubMed1988

Reduction of protein intake decreases glomerular filtration rate in young type 1 (insulin-dependent) diabetic patients mainly in hyperfiltering patients.

The influence of different protein intake on renal function was studied in 16 Type 1 (insulin-dependent) diabetic patients, aged 15-23 years, with onset of diabetes before puberty and with a duration of diabetes between 5 and 20 years. The glomerular filtration rate, renal plasma flow, albumin excretion rate, and blood pressure were examined in a cross-over randomised order after 10 days on isocaloric diets with either 10% (i.e. 0.9 +/- 0.06 g.kg-1.day-1) or 20% (1.9 +/- 0.1 g.kg-1.day-1) of the calories as protein, the latter being equal to the recommended diet. Dietary compliance was evaluated using fractional phosphate excretion and overnight urea excretion. Glomerular filtration rate was lower after the low-protein diet compared to the usual protein diet (p less than 0.001). Patients with glomerular filtration rate above +2 SD of the normal mean on the usual protein diet (n = 6) exhibited the steepest fall in glomerular filtration rate with a mean decrease of 20 ml/min compared to 7 ml/min in those with initially normal glomerular filtration (p = 0.01). Filtration fraction tended to decrease on low protein diet, more so in initially hyperfiltering patients (p = 0.09). Renal plasma flow remained unchanged. In patients with elevated glomerular filtration rate on usual protein diet, albumin excretion rate and systolic, but not diastolic blood pressure, were decreased on low protein diet (p = 0.03 and p = 0.01, respectively) but not in initially normal-filtering patients. Mean blood glucose and serum fructosamine were unchanged on both diets.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1994

Vortex flow filtration of mammalian and insect cells.

The use of vortex flow filtration for harvesting cells or conditioned medium from large scale bioreactors has proven to be an efficient, low shear method of cell concentration and conditioned medium clarification. Several 8-10 L batches of the human histiocytic lymphoma U-937 cell line (ATCC CRL 1593) were concentrated to less than 1 L by vortex flow filtration through a 3.0 microns membrane. An aggressive filtration regimen caused a 17% loss of cell viability and a 32% loss of IL-4 receptor binding capacity when compared to a batch centrifuged control. A reduction of the rotor speed from 1500 to 500 RPM and reduction of system back pressure from 10 to 0 PSIG resulted in cell viability and IL-4 binding capacity comparable to the control. Several 10 L batches of baculovirus infected Sf-9 cells were also concentrated to less than 1 L by vortex flow filtration through a 3.0 microns membrane. SDS-PAGE analysis of filtrate samples showed that aggressive filtration caused cell damage which led to contamination of the process stream by cellular lysate. When rotor speed was reduced to 500 RPM and system back pressure was reduced to 0 PSIG, the amount of contaminating lysate proteins in filtrate samples was comparable to a batch centrifuged control.

Animals↗

PubMed1991

Fast sampling, rapid filtration apparatus: principal characteristics and validation from studies of D-glucose transport in human jejunal brush-border membrane vesicles.

Kinetic data in (brush-border) membrane vesicles which rely on the validity of the initial rate assumption for their interpretation and depend on tracer flux studies using the rapid filtration technique for their experimental measurement have been limited to some extent by the absence of techniques that would allow for real-time data analysis. In this paper, we report on our successful design of a fast sampling, rapid filtration apparatus (FSRFA) which seems to fill up this technical gap since showing the following characteristics: (i) rapid injection (5 msec) and mixing (less than 100 msec) of small amounts of vesicles (10-40 microliters) with an incubation medium (0.2-1.0 ml); (ii) fast (20 to 80 msec depending on the sample volume) and multiple (up to 18 samples at a maximal rate of 4 sec) sampling of the uptake mixture followed by rapid quenching in the stop solution (approximately 5 msec) according to a predetermined time schedule (any time combination from 0.25 to 9999 sec); and (iii) fast, automated, and sampling-synchronized filtration and washings of the quenched uptake medium (only 15-20 sec are necessary for the first filtration followed by two washings and extra filtrations). As demonstrated using adult human jejunal brush-border membrane vesicles and Na(+)-D-glucose cotransport as models, the FSRFA accurately reproduces the manual aspects of the rapid filtration technique while allowing for very precise initial rate determinations. Moreover, the FSRFA has also been designed to provide as much versatility as possible and, in its present version, allows for a very precise control of the incubation temperature and also permits a few efflux protocols to be performed. Finally, its modular design, which separates the fast sampling unit from the rapid filtration device, should help in extending its use to fields other than transport measurement.

Biological Transport↗

PubMed2005

Coupling of sequencing batch reactor and mesh filtration: operational parameters and wastewater treatment performance.

Wastewater treatment performance of the combined process of sequencing batch reactor (SBR) and mesh filtration bio-reactor was investigated with a synthetic wastewater. In this system, the filtration was performed only by the water level difference between the reactor and the effluent port, with the help of a sludge layer which accumulated on the mesh filter. A half volume of the mixed liquor was filtrated for ca. 1 h, and the filtration time was not affected by the initial pressure within the range of 0.5-2.0 m-H2O. Since the mesh filter could effectively reject the biomasses in the reactor, the effluents contained SS of less than 1 mg/L and BOD of less than 10 mg/L under continuous or intermittent aeration conditions. Nitrogen was also removed effectively with the adjustment of aeration time under the intermittent aeration conditions. The results obtained in this work indicate that mesh filtration could be effectively combined with SBR and improve the performance of SBR. In addition, it was shown that the performance of the mesh filtration such as filtration time and solids separation was influenced significantly by the saccharide content in the exocellular polymer of the activated sludge.

Biopolymers↗

PubMed2001

One-dimensional filtration of pharmaceutical grade phyllosilicate dispersions.

The filtration behaviour of some clay-water dispersions was studied. Two Spanish fibrous phyllosilicates (sepiolite from Vicálvaro and palygorskite from Turón) and a commercial bentonite (Bentopharm UK) with similar sizes and different morphologies (fibrous and/or laminar) were selected as model clays. Sepiolite from Vicálvaro is an almost pure fibrous sample, Bentopharm presents a high amount of laminar particles and palygorskite from Turón is made up of similar percentages of laminar and fibrous particles. The disperse systems were made up using a rotor-stator mixer working at two different mixing rates (1000 and 8000 rpm), for periods of 1 and 10 min. Filtration measurements were taken and the corresponding filtration curves obtained. Finally, the desorptivity (S) of the filtration cakes was calculated and correlated to the textural characteristics of the materials, the solid fraction and mixing conditions. Filtration behaviour of the dispersions depended on all three of these factors. Laminar dispersions presented lower S values than fibrous dispersions. In the 2% w/v dispersions the bridging forces between particles did not permit formation of an interconnected network as in 10% w/v dispersions and, consequently, filtration times increased with the solid fraction (i.e. S values decreased). Regarding stability to pH changes, the results showed that filtration behaviour was highly sensitive to basic pH in the fibrous clay dispersions and almost insensitive in the laminar clay dispersions.

Aluminum Silicates↗

PubMed2001

Filtration artifacts caused by overloading membrane filters.

The conventional practice of using 0.45 or 0.40 microm membranes to distinguish between the particulate and dissolved phases in natural waters neglects the importance of colloids. Many of the colloids in natural waters pass through 0.45 or 0.40 microm membranes, but a significant fraction at the upper end of the colloidal particle size range is retained. Membrane clogging during filtration decreases the effective pore size and can cause the retention of increasing amounts of colloids. This filtration artifact can cause serious errors in sampling and in assigning trace metals to various particle size classes. We evaluated the effect of membrane loading for two common membrane types (0.45 microm Millipore Durapore and 0.40 microm Nuclepore) on the retention of colloidal Fe, Al, Mn, and OM in three Connecticut rivers. In addition, we used a 1.0 microm Nuclepore membrane to estimate the amount of colloids in the 0.40-1.0 microm size fraction that are retained by membranes during conventional filtration. All samples were collected with clean techniques, and all filtrations were carried out in a class 100 clean room. A peristaltic pump, set at an initial flow rate of 120 mL/min, was used to pump samples through 47 mm diameter inline Teflon filter holders. Back pressure and flow rate were monitored during filtration, and both are good indicators for the onset of membrane clogging. The results show a consistent correlation between increasing back pressure and decreasing concentration of colloidal Fe and sometimes Al, Mn, and OM in the filtrate for all membrane types. Although the shape of the loading-retention curves varied dramatically by site and by membrane type, the essential relationship between back pressure, flow rate, and filtration artifacts during membrane clogging remained the same.

Artifacts↗

PubMed1980

Long-term regulation of arterial pressure, glomerular filtration and renal sodium reabsorption by angiotensin II in dogs.

1. This study was designed to quantify the role of angiotensin II in determining the chronic relationships between arterial pressure, renal haemodynamics and sodium excretion. 2. In six control dogs sodium balance was achieved during chronic increases in sodium intake from 5 to 495 mmol/day with small increases in arterial pressure (7mmHg), moderate increases in glomerular filtration rate (19%) and decreases in filtration fraction. Similar increases in sodium intake in dogs whose circulating levels of angiotensin II were fixed, due to a constant intravenous infusion of 4.85 pmol of angiotensin II min-1 kg-1, caused large increases in arterial pressure (42%), glomerular filtration rate (31%), filtration fraction and calculated renal sodium reabsorption above control. In six dogs whose angiotensin II formation was blocked by SQ 14 225, sodium balance at intakes of 5-80 mmol/day occurred at reduced arterial pressure, glomerular filtration rate, filtration fraction and sodium reabsorption although plasma aldosterone concentration was not substantially different from that in control dogs. At sodium intakes above 240 mmoL/day arterial pressure was not altered by SQ 14 225. 3. These data indicate that during chronic variations in sodium intake angiotensin II plays a major role, independently of changes in plasma aldosterone concentration, in allowing sodium balance without large fluctuations in glomerular filtration rate or arterial pressure. The mechanism whereby angiotensin II conserves sodium chronically is through increased sodium reabsorption, since steady-state sodium reabsorption was increased by angiotensin II and decreased by SQ 14 225.

Aldosterone↗

PubMed1997

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 degrees C, and plasma frozen for 1 year with nonfiltered blood components as control. RESULTS: All counts of white blood cells after filtration were < 1 x 10(6) 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.

Blood Preservation↗