Apheresis Platelet Concentrates Research Articles

Amotosalen photochemical inactivation of severe acute respiratory syndrome coronavirus in human platelet concentrates.

summary. A novel human coronavirus causing severe acute respiratory syndrome (SARS) emerged in epidemic form in early 2003 in China and spread worldwide in a few months. Every newly emerging human pathogen is of concern for the safety of the blood supply during and after an epidemic crisis. For this purpose, we have evaluated the inactivation of SARS‐coronavirus (CoV) in platelet concentrates using an approved pathogen inactivation device, the INTERCEPT Blood System. Apheresis platelet concentrates (APCs) were inoculated with approximately 106 pfu mL−1 of either Urbani or HSR1 isolates of SARS‐CoV. The inoculated units were mixed with 150 µm amotosalen and illuminated with 3 J cm−2 UV‐A light. The viral titres were determined by plaque formation in Vero E6 cells. Mixing SARS‐CoV with APC in the absence of any treatment decreased viral infectivity by approximately 0·5–1 log10. Following photochemical treatment, SARS‐CoV was consistently inactivated to the limit of detection in seven independent APC units. No infectious virus was detected after treatment when up to one‐third of the APC unit was assayed, demonstrating a mean log10‐reduction of >6·2. Potent inactivation of SARS‐CoV therefore extends the capability of the INTERCEPT Blood System in inactivating a broad spectrum of human pathogens including recently emerging respiratory viruses.

Optimized Scansystem™ platelet kit for bacterial detection with enhanced sensitivity: detection within 24 h after spiking

The prevention and detection of bacterial contamination of platelet concentrates remains a major challenge for transfusion medicine. To be suitable for blood-transfusion services, the contamination detection method must be highly sensitive, easy to perform and preferably of low cost. In this spiking study, we evaluated the new optimized Scansystem Platelet Kit detection method for use on apheresis platelets. Apheresis platelet concentrates (APCs) were individually spiked with 10 colony-forming units (CFU)/ml of one of 10 different strains of bacteria. The spiked APCs were analysed at specific time-points during incubation by using the optimized Scansystem Platelet Kit. Bacterial enumeration was performed by plating onto blood agar. All the bacterial strains tested were detected by using the optimized Scansystem Platelet Kit when sampled 24 h after spiking. Compared to the Scansystem standard kit, sensitivity was increased to < 50 CFU/ml. The identity of the spiked bacteria was confirmed by Gram staining and DNA fingerprinting. The optimized Scansystem Platelet Kit was able to reliably detect, within 70 min, 10 transfusion-relevant bacterial species in APCs when a sample volume was taken 24 h after spiking. This is the first study carried out by using the optimized Scansystem bacterial detection that was found to have an enhanced sensitivity compared to the standard kit.

Additive effects between platelet concentrates and desmopressin in antagonizing the platelet glycoprotein IIb/IIIa inhibitor eptifibatide

Platelet (PLT) glycoprotein (GP) IIb/IIIa receptor antagonists have demonstrated efficacy in decreasing ischemic complications of percutaneous coronary intervention and/or unstable angina. In case of bleeding, the drug can be stopped and PLT transfusions can be given. This crossover study tested the additive effects of PLT concentrates (PCs) after desmopressin (DDAVP) infusion in antagonizing the anti-PLT effects of GPIIb/IIIa inhibitors and aspirin. After eptifibatide and aspirin infusion (at standard dosages), 10 healthy volunteers received DDAVP or placebo. Thereafter, increasing amounts of PLTs from fresh single-donor apheresis concentrates were added in vitro to blood samples of all volunteers to increase PLT counts by 30 x 10(9), 60 x 10(9), or 120 x 10(9) per L. Adding platelets in vitro further improved PLT function after DDAVP: it shortened collagen-adenosine diphosphate closure times (p < 0.01), to normal ranges as measured by the PLT function analyzer (PFA-100). In contrast, normal PLT function could not be restored even when PLT counts were increased by 50 percent (120 x 10(9)/L) in the placebo group. Combined use of PLTs from fresh apheresis PC and DDAVP additively enhances recovery of normal PLT function after eptifibatide infusion. Such a strategy may help to avoid excessive transfusion of PC.

The effect of the interruption of agitation on platelet quality during storage for transfusion.

A considerable amount of data and the CFR suggest that platelet concentrates (PCs) should be stored with continuous, gentle agitation before transfusion. However, there are only limited data concerning the mechanisms of platelet damage that may occur when agitation is interrupted, and there are no CFR guidelines concerning shipment between periods of storage. PCs were prepared by the platelet-rich plasma method and stored for 5 days at 20 to 24 degrees C; agitation was interrupted for 1 to 3 days either by simply stopping the agitator or by placing the PCs in a stationary shipping container. Measurements of platelet metabolism and quality were made during storage and on Day 5. With interruption on the agitator, the production of lactic acid was increased during the interruption in proportion to the number of platelets in the PC and the duration of the interruption. The pO(2) was increased during agitation interruption, which suggested a decline in oxygen utilization. With the use of the hypotonic shock response and the extent of shape change as reflections of platelet quality, there was no evidence of platelet damage unless the pH fell to or below 6.5. No PC reached this level after an interruption of agitation for only 1 day, irrespective of which day was chosen for interruption. PCs whose agitation was interrupted for 2 and 3 days were at risk of having a pH less than 6.5 if their contents were greater than 1.25 x 10(11) and 0.75 x 10(11) platelets, respectively. Interruption of agitation for 1 day in the shipping container produced results essentially identical to those produced by interruption on the agitator. Interruption of agitation of PCs for 1 day, either on the agitator or in the shipping container, produces no platelet damage measurable by these in vitro techniques. However, an interruption of agitation for 2 days can result in significant damage in some components. Further studies will be required to learn more about the mechanisms that lead to the metabolic changes described and to determine if the same generalizations apply to apheresis PCs and PCs prepared from pooled buffy coats.

Platelet storage media

Platelet additive solutions (PASs) can be used as a substitute for plasma for the storage of platelet concentrates (PCs) in order to recover plasma for other purposes, to avoid transfusion of large volumes of plasma to patients, to improve storage conditions, and to make possible photochemical treatment for viral inactivation of PCs. The effects on platelet metabolism associated with different factors and compounds in PAS are only partly known. Available studies suggest that: (1) The presence of glucose in the platelet storage medium during the entire storage period is necessary for platelet metabolism. (2) Acetate is used as a substrate for platelet metabolism reducing production of lactate by platelets. By formation of bicarbonate, it maintains stable pH levels during storage. (3) The fall in pH can be rapid in PAS-containing media, due to the very limited buffering capacity of PAS compared with that of plasma. (4) Platelets stored in PAS at a citrate concentration of 8 mmol/l produce only half the quantity of lactate as that of platelets at 14–26 mmol/l of citrate. (5) Free fatty acids from plasma can be used as substrate for platelet metabolism and are supposed to be made available by the hydrolysis of plasma triglycerides. (6) For apheresis PCs with ACD anticoagulant, the presence of phosphate in PAS seems to be a critical factor to avoid low adenine nucleotide levels during storage. The results of available studies suggest that PAS for storing platelets has a great potential for wide use in transfusion medicine. A number of interesting questions regarding the effects of different compounds in PAS are still to be answered. It is expected that answers to these questions will be provided over the next few years.

Prion protein release in apheresis platelet concentrates is associated with platelet activation and lysis

Studies using a time-resolved fluoroimmuno-assay (DELFIA®) have shown that platelets and plasma are the main compartments of the normal isoform of prion protein (PrPc) in human blood. The aim of the present study was to monitor PrPc levels in various fractions of apheresis platelet concentrates (PC) during storage and to assess the association of this release with α granule protein β-thrombo-globulin (BTG) and cytoplasmic lactate dehydrogenase (LDH) as cell activation and cell lysis markers, respectively. Six apheresis PC were obtained from volunteer donors using Haemonetics MCS and stored up to 10 days. 7–9 mL samples were aseptically collected from each PC on days 1, 2, 3, 4, 5, 8, and 10 of storage. Platelet poor plasma (PPP) and platelets (P) were prepared and the PPP split into two equal fractions, one of which was centrifuged at 40,000g for 2 h at 4 °C to remove microparticles (MP) [high spun plasma (HSP)]. The results showed that the mean overall levels of PrPc during storage remained within 15% of day 1 levels. In contrast, the mean levels in P significantly decreased to 46% day 1 levels by day 10 of storage (P < 0·01), while the corresponding levels in plasma significantly rose by up to 329% (P < 0·01). Moreover, although MP-bound PrPc was released during storage, it was increasingly superceded by soluble prion protein. PrPc and BTG release exhibited very similar patterns, both showing a significant rise in PPP and HSP (P < 0·01). In contrast, LDH showed a significant rise in HSP only towards the end of the storage period (P < 0·01). These results indicate that PrPc is released from platelets during storage of PCs and that this release is probably due mainly to platelet activation and α-granule release in the first few days of storage. The release of PrPc is apparently reinforced through cell lysis, and is increasingly comprised of soluble prion proteins, at longer storage periods.

Are All Leucodepleted Platelet Concentrates Equivalent?

Background and Objectives: A number of technologies are available for the production of leucocyte–depleted platelet concentrates (PCs). This study compared the characteristics of PCs prepared by three commonly used techniques. Materials and Methods: In total, fifteen units of leucoyte–depleted PCs prepared by the Cobe LRS Turbo apheresis system, Haemonetics MCS+ with in–line filter and filtration of PCs derived from pooled buffy coats (BCs) were transferred into the same standard container. Markers to assess status/activation and microvesiculation of platelets as well as platelet injury were measured. Results: pH was well maintained in all types of PCs. The expression of CD62P was higher in Cobe LRS Turbo on day 1 but became equivalent between the three methods on day 5. A significant correlation was found between the expression of CD62P on platelet surface and soluble CD62P in the plasma. The degree of phosphatidylserine (PS) exposure was slightly higher in Cobe LRS Turbo and BC–PCs than Haemonetics MCS+ on day 1. However, on day 5 both apheresis PC values were higher than BC–PCs. A significant correlation was found between PS exposure and microvesiculation. Conclusion: Leucodepleted PCs prepared by the three methods were different in terms of storage lesion and microvesiculation. The clinical significance of these findings remains to be investigated.

Are All Leucodepleted Platelet Concentrates Equivalent?

Abstract Background and Objectives: A number of technologies are available for the production of leucocyte‐depleted platelet concentrates (PCs). This study compared the characteristics of PCs prepared by three commonly used techniques. Materials and Methods: In total, fifteen units of leucoyte‐depleted PCs prepared by the Cobe LRS Turbo apheresis system, Haemonetics MCS+ with in‐line filter and filtration of PCs derived from pooled buffy coats (BCs) were transferred into the same standard container. Markers to assess status/activation and microvesiculation of platelets as well as platelet injury were measured. Results: pH was well maintained in all types of PCs. The expression of CD62P was higher in Cobe LRS Turbo on day 1 but became equivalent between the three methods on day 5. A significant correlation was found between the expression of CD62P on platelet surface and soluble CD62P in the plasma. The degree of phosphatidylserine (PS) exposure was slightly higher in Cobe LRS Turbo and BC‐PCs than Haemonetics MCS+ on day 1. However, on day 5 both apheresis PC values were higher than BC‐PCs. A significant correlation was found between PS exposure and microvesiculation. Conclusion: Leucodepleted PCs prepared by the three methods were different in terms of storage lesion and microvesiculation. The clinical significance of these findings remains to be investigated.

Storage of Platelets in Additive Solutions: Effects of Phosphate

Background and Objectives: In a previous study, low adenine nucleotide levels and a reduced rate of glycolysis were found in platelet concentrates (PCs) prepared by apheresis and stored in a platelet additive solution (PAS). Our objective was to investigate whether the use of PAS with or without phosphate can influence platelet metabolism in a similar way. Materials and Methods: The in vitro effects of storage in either plasma or a PAS (T–Sol or PAS–III, both containing citrate, acetate and sodium chloride, PAS–III containing also phosphate) of buffy–coat–derived pooled platelet concentrates (BC–PCs) and apheresis platelets were investigated. The use of PAS implies inclusion of some plasma (20 or 35%). Paired studies over 7 days included investigation of cell counts, pH, PO₂, PCO₂, bicarbonate, glucose, lactate, adenine nucleotides, and extracellular adenylate kinase activity as a marker for disintegration of platelets. The expected concentration of phosphate in T–Sol is 0.6– 1.8 mmol/l (with CPD plasma) and 0.2–0.6 mmol/l (with ACD plasma), and in PAS–III, 15–25 mmol/l (calculated values). Results: BC–PCs were compared during storage in 35% CPD plasma and 65% PAS (T–Sol or PAS–III) (experiment 1), or alternatively 20% CPD plasma and 80% PAS (T–Sol or PAS–III) (experiment 3). In both studies, PAS–III shows similar and significantly higher rates of glycolysis in terms of consumption of glucose (0.06 vs. 0.04 mmol/day/10¹¹ platelets) and production of lactate (0.11 vs. 0.07 mmol/day/10¹¹ platelets) compared with T–Sol. Levels of pH and adenine nucleotides were similar when 35% plasma was used. With only 20% plasma, significantly higher levels of adenine nucleotides were found with PAS–III compared to T–Sol. The storage of apheresis platelets in 35% ACD plasma and 65% PAS (either T–Sol or PAS–III) (experiment 5) gave significantly higher values for PAS–III compared to T–Sol with regard to consumption of glucose (0.08 vs. 0.06 mmol/day/10¹¹ platelets), production of lactate (0.14 vs. 0.11 mmol/ day/10¹¹ platelets) and adenine nucleotide levels. Conclusion: With respect to apheresis PCs stored in media containing ACD plasma, our results suggest that the differences found are related to the concentration of phosphate. The results for BC–PCs stored in media containing CPD plasma suggest that PAS–III is preferable to T–Sol as the PAS at plasma concentrations below 35%. The mechanism behind the phenomena observed with BC–PCs is not known.

Storage of Platelets in Additive Solutions: Effects of Phosphate

Background and Objectives: In a previous study, low adenine nucleotide levels and a reduced rate of glycolysis were found in platelet concentrates (PCs) prepared by apheresis and stored in a platelet additive solution (PAS). Our objective was to investigate whether the use of PAS with or without phosphate can influence platelet metabolism in a similar way. Materials and Methods: The in vitro effects of storage in either plasma or a PAS (T-Sol or PAS-III, both containing citrate, acetate and sodium chloride, PAS-III containing also phosphate) of buffy-coat-de rived pooled platelet concentrates (BC PCs) and apheresis platelets were investigated. The use of PAS implies inclusion of some plasma (20 or 35%). Paired studies over 7 days included investigation of cell counts, pH, PO2, PCO2, bicarbonate, glucose, lactate, adenine nucleotides, and extracellular adenylate kinase activity as a marker for disintegration of platelets. The expected concentration of phosphate in T-Sol is 0.6–1.8 mmol/I (with CPD plasma) and 0.2–0.6 mmol/l (with ACD plasma), and in PAS-III, 15–25 mmol/I (calculated values). Results: BC-PCs were compared during storage in 35% CPD plasma and 65% PAS (T-Sol or PAS-III) (experiment 1), or alternatively 20% CPD plasma and 80% PAS (T-Sol or PAS-III) (experiment 3). In both studies, PAS-III shows similar and significantly higher rates of glycolysis in terms of consumption of glucose (0.06 vs. 0.04 mmol/day/1011 platelets) and production of lactate (0.11 vs. 0.07 mmol/day/1011 platelets) compared with T Sol. Levels of pH and adenine nucleotides were similar when 35% plasma was used. With only 20% plasma, significantly higher levels of adenine nucleotides were found with PAS-III compared to T-Sol. The storage of apheresis platelets in 35% ACD plasma and 65% PAS (either, T-Sol or PAS-III (experiment 5) gave significantly higher values for PAS-III compared to T-Sol with regard to consumption of glucose (0.08 vs. 0.06 mmol/day/1011 platelets), production of lactate (0.14 vs. 0.11 mmol/day/1011 platelets) and adenine nucleotide levels. Conclusion: With respect to apheresis PCs stored in media containing ACD plasma, our results suggest that the differences found are related to the concentration of phosphate. The results for BC-PCs stored in media containing CPD plasma suggest that PAS-III is preferable to T-Sol as the PAS at plasma concentrations below 35%. The mechanism behind the phenomena observed with BC-PCs is not known.

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

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

Clinical Evaluation of Transfusion of Prestorage-Leukoreduced Apheresis Platelets

With increased use of platelet concentrate (PC) in recent years, adverse reactions to PC transfusion have received much clinical attention. Most of these reactions stem from white blood cells (WBC) contaminating the transfused PC. Several are thought to be preventable by removing WBC before PC storage. Methods: We routinely filtered apheresis PC either during collection or immediately afterwards and monitored various indicators of platelet quality during storage. After transfusion to patients, transfusion efficacy and the type, severity, and frequency of posttransfusion side effects were compared with those of a control group in which PC was filtered at the bedside. Results: Prestorage-filtered PC contained an average of 3.1±0.7 × 10¹¹ platelets and 0.9±1.2 × 10⁶ contaminating leukocytes. Measurement of platelet function and metabolic indicators revealed normal values throughout the storage period. CD62 measurement revealed no undue platelet activation after filtration or during the storage period. Cytokine, histamine, bradykinin, and complement levels showed no significant increase after filtration or during storage. Transfusion efficacy and overall side effect incidence rates were similar for the prestorage- and bedside-filtered groups, but reactions of the bedside-filtered group included serious reactions such as breathing difficulties and shock. No serious reactions were noted in the prestorage-filtered group. Conclusion: Filtering PC before storage has no adverse effect on PC quality and may reduce the severity of post transfusion side effects.

Clinical Evaluation of Transfusion of Prestorage‐Leukoreduced Apheresis Platelets

AbstractWith increased use of platelet concentrate (PC) in recent years, adverse reactions to PC transfusion have received much clinical attention. Most of these reactions stem from white blood cells (WBC) contaminating the transfused PC. Several are thought to be preventable by removing WBC before PC storage. Methods: We routinely filtered apheresis PC either during collection or immediately afterwards and monitored various indicators of platelet quality during storage. After transfusion to patients, transfusion efficacy and the type, severity, and frequency of posttransfusion side effects were compared with those of a control group in which PC was filtered at the bedside. Results: Prestorage‐filtered PC contained an average of 3.1±0.7×1011 platelets and 0.9±1.2×106 contaminating leukocytes. Messurement of platelet function and metabolic indicators revealed normal values throughout the storage period. CD62 measurement revealed no undue platelet activation after filtration or during the storage period. Cytokine, histamine, bradykinin, and complement levels showed no significant increase after filtration or during storage. Transfusion efficacy and overall side effect incidence rates were similar for the prestorage‐and bedside‐filtered groups, but reactions of the bedside‐filtered group included serious reactions such as breathing difficulties and shock. No serious reactions were noted in the prestorage‐filtered group. Conclusion: Filtering PC before storage has no adverse effect on PC quality and may reduce the severity of post transfusion side effects.

Platelet Transfusion: A Dose-Response Study

AbstractEarly recommendations on prophylactic transfusion of thrombocytopenic patients involved a standard platelet dose of about 0.5 × 1011/10 kg body weight. Given the lack of data supporting this dose, we prospectively studied the dose response to platelet transfusions in adults and children with hematologic malignancies. Each patient received, in similar clinical conditions, a medium, high, and very high dose of fresh (< 24 hours old) ABO-compatible platelets, in the form of apheresis platelet concentrates (APC). For the adults, the medium dose was defined as APC containing between 4 and 6 × 1011 platelets, the high dose between 6 and 8 × 1011, and the very high dose > 8 × 1011; for the children, the three doses corresponded to 2 to 4, 4 to 6, and > 6 × 1011 platelets. The end points were the platelet increment, platelet recovery, and the transfusion interval, and the results were compared with a paired t-test. Sixty-nine adults and 13 children could be assessed. Recoveries in the adults were similar with the three doses (from 28% to 30%), but the high and very high doses led to a significantly better platelet increment (52 and 61 × 109/L, respectively) than the medium dose (33 × 109/L, P < .01). The main difference was in the transfusion interval, which increased with the dose of platelets transfused, from 2.6 days with the medium dose to 3.3 and 4.1 days with the high and very high doses, respectively (P< .01). The positive effect of the high dose was observed regardless of pretransfusional clinical status, but was more marked in patients with no clinical factors known to impair platelet recovery. In these patients, a platelet dose of 0.07 × 1011 per kg of body weight led to a transfusion interval of more than 2 days in 95% of cases. In patients with clinical factors favoring platelet consumption, the proportion of transfusions yielding an optimal platelet increment and transfusion interval increased with the dose of platelets.The platelet dose-effect was also significant in the children, in whom the high and very high doses led to 1.5-fold to twofold higher posttransfusion platelet counts and transfusion intervals. We conclude that transfusion of high platelet doses can reduce the number of platelet concentrates required by thrombocytopenic patients and significantly reduce donor exposure.© 1998 by The American Society of Hematology.

Platelet Transfusion: A Dose-Response Study

Early recommendations on prophylactic transfusion of thrombocytopenic patients involved a standard platelet dose of about 0.5 × 1011/10 kg body weight. Given the lack of data supporting this dose, we prospectively studied the dose response to platelet transfusions in adults and children with hematologic malignancies. Each patient received, in similar clinical conditions, a medium, high, and very high dose of fresh (&lt; 24 hours old) ABO-compatible platelets, in the form of apheresis platelet concentrates (APC). For the adults, the medium dose was defined as APC containing between 4 and 6 × 1011 platelets, the high dose between 6 and 8 × 1011, and the very high dose &gt; 8 × 1011; for the children, the three doses corresponded to 2 to 4, 4 to 6, and &gt; 6 × 1011 platelets. The end points were the platelet increment, platelet recovery, and the transfusion interval, and the results were compared with a paired t-test. Sixty-nine adults and 13 children could be assessed. Recoveries in the adults were similar with the three doses (from 28% to 30%), but the high and very high doses led to a significantly better platelet increment (52 and 61 × 109/L, respectively) than the medium dose (33 × 109/L, P &lt; .01). The main difference was in the transfusion interval, which increased with the dose of platelets transfused, from 2.6 days with the medium dose to 3.3 and 4.1 days with the high and very high doses, respectively (P&lt; .01). The positive effect of the high dose was observed regardless of pretransfusional clinical status, but was more marked in patients with no clinical factors known to impair platelet recovery. In these patients, a platelet dose of 0.07 × 1011 per kg of body weight led to a transfusion interval of more than 2 days in 95% of cases. In patients with clinical factors favoring platelet consumption, the proportion of transfusions yielding an optimal platelet increment and transfusion interval increased with the dose of platelets.The platelet dose-effect was also significant in the children, in whom the high and very high doses led to 1.5-fold to twofold higher posttransfusion platelet counts and transfusion intervals. We conclude that transfusion of high platelet doses can reduce the number of platelet concentrates required by thrombocytopenic patients and significantly reduce donor exposure. © 1998 by The American Society of Hematology.

White cell subsets in apheresis and filtered platelet concentrates.

White cell (WBC)-reduced platelet concentrates (PCs) are defined by their absolute WBC count, a criterion which provides no information regarding the various WBC subsets contained in the PC. These heterogeneous cells are known to mediate different physiologic and pathophysiologic functions and account for distinct adverse transfusion responses. This study describes a method which allows the detection and quantification of these subsets and characterizes their presence in a variety of platelet components. Random-donor pooled PCs (RD PCs) and single-donor apheresis PCs (SD PCs) were studied. RD PCs consisting of 6 units of 2- to 3-day old PCs were randomly assigned to be filtered with one of four WBC-reduction filters from three different manufacturers (n=34). The residual WBCs were pelleted by centrifugation and isolated on a density gradient. The various WBC subsets were quantified by flow cytometry in unfiltered and filtered PCs using fluorescence and two-angle light scatter. SD PCs obtained with two manufacturer's systems and three processing protocols (n=30) were studied in like manner. WBC counts for non-WBC-reduced PCs averaged 3 x 10(8) in RD PCs and ranged from 8.6 to 9.6 x 10(6) per SD PC. Residual WBC counts in filtered PCs ranged from 2.3 x 10(4) to 2.2 x 10(5) and those in WBC-reduced SD PCs averaged 2.2 x 10(5) per unit. The data demonstrate significant phenotypic differences among PCs produced with various procedures. All SD PCs and two of four filtered RD PCs contained five WBC populations including granulocytes and monocytes, while RD PCs filtered with the remaining manufacturer's devices contained only lymphocytes. The data confirm that distinct phenotypic differences exist among PCs prepared with different devices and/or procedures. It is suggested that as for non-generic pharmaceuticals, the clinical benefits of these various PCs should be individually proved.

Quality and Safety of Platelet Apheresis Concentrates Produced with a New Leukocyte Reduction System

Abstract Objectives: Contaminating white blood cells (WBC) in apheresis platelet concentrates (PC) can cause a variety of adverse effects after platelet transfusion. To obtain PCs with low WBC contamination, a new leukoreduction system (LRS) utilizing ‘fluidized particle bed’ technology has recently been introduced. Methods: We prospectively examined the effect of LRS apheresis on the donor, the quality of the resulting PCs (n = 120), and the platelet increment in the corresponding recipients. Conventionally prepared apheresis PCs served as control group (n = 27). Platelet glycoproteins were examined by flow cytometry. Results: In LRS apheresis, we observed no serious adverse effects on the donors, but the postdonation absolute lymphocyte counts were reduced from 1,787±505/μl to 1,405±383/μl (p&lt;0.001). Comparable results were seen in non‐LRS donors. The collection efficiency of the LRS procedures was 50.0±7.6%, resulting in a yield of 4.3±1.0 × 1011 platelets/PC. In flow cytometry, platelet glycoproteins in LRS PCs were not elevated: mean fluorescence of CD62 (6±4) or CD63 (9±3) in comparison with non‐LRS PCs (mean fluorescence of CD62: 7±4, CD63: 8±3). Median leukocyte contamination of the LRS PCs was 0.41 × 105 (range 0.07–8.5) WBCs/unit. In 43 recipients, the 24‐hour corrected count increments after transfusion of LRS PCs (12,530±8,761) were essentially the same as those of 20 recipients of non‐LRS PCs (13,133±9,812; p = 0.75). Conclusions: LRS apheresis appears to be a safe procedure, which produced effective PCs with few contaminating leukocytes. With new apheresis technology, filtration of PCs may become superfluous.

Quality and Safety of Platelet Apheresis Concentrates Produced with a New Leukocyte Reduction System

Objectives: Contaminating white blood cells (WBC) in apheresis platelet concentrates (PC) can cause a variety of adverse effects after platelet transfusion. To obtain PCs with low WBC contamination, a new leukoreduction system (LRS) utilizing ‘fluidized particle bed’ technology has recently been introduced. Methods: We prospectively examined the effect of LRS apheresis on the donor, the quality of the resulting PCs (n = 120), and the platelet increment in the corresponding recipients. Conventionally prepared apheresis PCs served as control group (n = 27). Platelet glycoproteins were examined by flow cytometry. Results: In LRS apheresis, we observed no serious adverse effects on the donors, but the postdonation absolute lymphocyte counts were reduced from 1,787±505/μl to 1,405±383/μl (p < 0.001). Comparable results were seen in non-LRS donors. The collection efficiency of the LRS procedures was 50.0±7.6%, resulting in a yield of 4.3±1.0 × 10¹¹ platelets/PC. In flow cytometry, platelet glycoproteins in LRS PCs were not elevated: mean fluorescence of CD62 (6±4) or CD63 (9±3) in comparison with non-LRS PCs (mean fluorescence of CD62: 7±4, CD63: 8±3). Median leukocyte contamination of the LRS PCs was 0.41 × 10⁵ (range 0.07–8.5) WBCs/unit. In 43 recipients, the 24-hour corrected count increments after transfusion of LRS PCs (12,530±8,761) were essentially the same as those of 20 recipients of non-LRS PCs (13,133±9,812; p = 0.75). Conclusions: LRS apheresis appears to be a safe procedure, which produced effective PCs with few contaminating leukocytes. With new apheresis technology, filtration of PCs may become superfluous.

Effect of filtration and storage of platelet concentrates on the production of the chemotaxins C5a, interleukin 8, tumor necrosis factor alpha, and leukotriene B4.

The production in platelet concentrates (PCs) of C3 activation products (C3bc), terminal complement complex (TCC), and chemotaxins C5a, interleukin (IL)-8, tumor necrosis factor alpha (TNFalpha), and leukotriene B4 (LTB4) and the proposed reduction in concentration of the chemotaxins by white cell reduction were examined. Samples were collected from supernatants of PCs produced by apheresis (apheresis PCs) or from buffy coats (BC PCs) immediately after the production, after white cell-reduction filtration on Day 1, and after 5-day storage, and examined by enzyme immunoassays. Complement was activated in all PCs during storage, and the concentration of activation products was not influenced by prestorage filtration. In prestorage white cell-reduced BC PCs, only C3bc levels increased. Levels of IL-8, TNFalpha, and LTB4 increased during storage of apheresis PCs, but not in filtered units, except for LTB4. In contrast, levels of IL-8 decreased after storage of filtered BC PCs. C5a correlated significantly with IL-8, which also correlated with TNFalpha and LTB4. Both C5a and TNFalpha generation in apheresis PCs seem to induce white cell IL-8 production, which mediates cellular LTB4 release. Prestorage white cell reduction is recommended for reducing chemotactic cytokine and leukotriene levels in all PCs. Production of BC PCs is recommended to achieve less complement activation, which is not affected by filtration.

Differential induction of P‐selectin expression on platelets by two cell separators during plateletpheresis and the effect of gender on the release of soluble P‐selectin

Though a number of studies have elegantly characterized platelet activation during storage, less attention has been paid to the initial activation caused by different collection procedures. The effects of two blood cell separators on the initial activation of platelets were measured by flow cytometric analysis of P-selectin expression in 13 male donors on one cell separator (CS 3000 Plus) and 11 men and 9 women on the other (MCS 3P). In addition, the storage and release of soluble P-selectin (circulating P-selectin [cP-selectin]) by platelets were quantified, to determine whether the change in cP-selectin is a more sensitive marker for initial platelet activation, and the influence of gender on measured endpoints was evaluated. The CS 3000 Plus increased the percentage of P-selectin-positive platelets from a median of 3.4 percent before apheresis to 7.6 percent (p = 0.006) in platelet concentrates (PCs), whereas the MCS 3P did not (p = 0.002 between the two cell separators). When preapheresis cP-selectin levels were compared to those in apheresis PCs, cP-selectin increased from 51 to 101 ng per mL in plasma of CS 3000 Plus PCs, whereas cP-selectin levels increased from 53 to 78 ng per mL in MCS 3P PCs (men) and from 48 to 99 ng per mL in MSC 3P PCs (women) (p<0.005 for all). The relative increase in cP-selectin was higher in women than in men in MCS 3P PCs (p = 0.013). Concomitantly, the amount of P-selectin stored in platelets before apheresis decreased (p<0.025 for all). When donors undergoing apheresis on the MCS 3P were compared, the amount of P-selectin stored in the platelets of PCs was higher in men than women (p = 0.026). This trial shows 1) that initial activation of platelets obtained with the MCS 3P is less than that of platelets obtained with the CS 3000 Plus; 2) that the increase in cP-selectin is a more sensitive marker for initial platelet activation than the expression of P-selectin on the surface; and 3) that the relative amount of cP-selectin is higher in women than in men given the same stimulus. Differences in platelet activation by various cell separators and the sex of the donor may contribute to variability of PC quality.