The effects of leukodepletion on the generation and removal of microvesicles and prion protein in blood components.

Background: Universal leukodepletion (LD) has been implemented in the United Kingdom to reduce the risk of transfusion-transmitted variant Creutzfeldt-Jakob disease. If LD causes microvesiculation of blood cells, however, potentially infectious membrane-associated prion could reach the final products.

Study Design And Methods: We have measured microvesicles (MV) derived from red cells (RBC-MV), platelets (PLT-MV), and white blood cells (WBC-MV) and cellular prion protein (PrP(c)) in blood components produced by four whole-blood, five RBC, three PLT, and two plasma LD filters and three plateletpheresis techniques.

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.

Cytokine levels as performance indicators for white blood cell reduction of platelet concentrates.

Background And Objectives: With the implementation of universal white blood cell (WBC) reduction in the UK, in-process WBC-reduction filters for pooled buffy coat (BC)-derived platelet concentrates (PCs) and apheresis methods are used routinely for the production of WBC-reduced PCs. While these strategies meet the specification for WBC reduction (< 5 x 10(6) WBCs/unit), the products from these processes may differ depending on the process employed and its performance. The aim of this study was therefore to investigate whether PCs prepared using various WBC-reduction processes are sufficiently depleted of WBCs to limit cytokine accumulation during storage and to assess if cytokine levels detected in platelet products can serve as indicators of acceptable platelet activation as a result of the WBC-reduction process.

Red cell storage lesion assessed by the levels of potassium, haemoglobin and Annexin V in supernatants.

The conventional and a new marker of global cellular lesion (Annexin V) are used to assess the processing/storage-induced changes in four types of RBC and filtered blood at 4 degrees and 22 degrees C, stored for a period of 35 days, in multi-satellite packs. It appears that mechanical trauma and presence of leucocytes and residual platelets have potential to increase levels of all markers of storage lesion, but to a variable extend. We have also provided new evidence that multi-satellite packs can be safely used for up to 35 days for small volume transfusion to sick premature infants, in a well-managed system by administering several transfusions from the same donation, hence reducing donor exposure.

A platelet quality assessment scheme for comparing the performance of quality monitoring laboratories in the UK National Blood Service.

This exercise focused on performance of NBS quality monitoring establishments with respect to enumeration of low leucocyte and other quality indexes of platelet concentration. Paired identical leucodepleted platelet samples, spiked with WBC (20 cells/microl) in 'vacuette' or 'pouch' were assessed by participants (n = 20) on days 1, 2 and 5. For low WBC counting, all laboratories gave estimates within acceptable range (+/-25%) and good agreement between storage and assay methods was observed on days 1 and 2.

A national quality assessment scheme for counting residual leucocytes in unfixed leucodepleted products: the effect of standardisation and 48 hour storage.

Background: WBC counting, an essential part of quality monitoring of WBC-reduced blood components, is carried out logistically within 48-72 h of collection. The between-laboratory variability and effects of 24-48 h storage were investigated using three major counting technologies.

Study Design And Methods: Samples of RBC and platelets with WBC in the range 0-50/microl were transported by courier.

Validation of different enrichment strategies for analysis of leucocyte sub-populations: development and application of a new approach, based on leucofiltration.

Characterisation of the nature of leucodepletion failure, based on the analysis of leucocyte sub-populations, is an essential task for continual improvement in the clinical safety of blood components and for the selection of a safe and appropriate leucodepletion process. Such information is also critical for improving the quality of filters through an understanding of the mechanism of leucocyte removal filters. Unfortunately, the residual leucocytes of filtered blood components are around the sensitivity of current leucocyte-counting technologies, hence a need for an enrichment process.

Studies on the characterisation of the cause of leucoreduction failures, with particular reference to extra gatal events.

The causes of leucodepletion failure are multifactoral and can be related to haematological variability in blood donors or donation, defective filters, poor specimen handling or ageing, and/or the presence of non-adhering leucocyte/platelets. Since refiltering removes all types of leucocytes, including the populations appearing as extra gated events, we have developed a practical method for refiltering the failed leucodepleted components on standard filters and back-flushing the second filter to assess the nature of the WBC sub-population. In practice, recovered leucocytes from red cell filters and whole blood mainly consist of neutrophils.

Cytokines as quality indicators of leucoreduced red cell concentrates.

Different types of filters are currently used for leucodepletion of red cell concentrates. These filters meet the specification for leucoreduction (<5 x 10(6) leucocytes/ATD) but the quality of the final product may differ depending on the performance of the filters for effective removal of both leucocytes, platelets and possibly cytokines which are associated with transfusion reactions. We measured the levels of three representative cytokines: IL-8, RANTES and TGF-beta1 in red cell concentrates prior to and subsequent to the filtration procedure on day 1 and after a storage period of 35 days.

The quality of MCS+ version C2 double dose platelet concentrate with leucodepletion through a continuous filtration process.

182 full double donations were collected, using 7-9 cycles with an in-house guideline based on donor HCT, and platelet count. 95.6% of donations were within specifications for platelet yield and 100% were leucodepleted.

What's happening? The quality of methylene blue treated FFP and cryo.

It is currently unclear to what degree methylene blue in combination with removal, of cells from plasma, by filter, can directly influence the loss of active components of plasma and whether the co-precipitation of FVIII/vWf with fibrinogen/fibronectin is affected by combined methylene blue and light treatment (MBLT). These questions are investigated using the Fenwal system. Our results indicate that up to 15% of the FVIII and IX are lost due to exposure of plasma to filters and methylene blue (MB).

Residual red cell and platelet content in WBC-reduced plasma measured by a novel flow cytometric method.

Background: The levels of residual red blood cells (RBC) and platelets (PLT) in WBC-reduced plasma are often below the lower detection limit of automated blood cell counters. This study established a novel flow cytometric method for the enumeration of residual RBC and PLT in plasma. Furthermore, their levels in WBC-reduced plasma prepared by using various filters were investigated.

The role of maternal serum C-reactive protein and white blood cell count in the prediction of chorioamnionitis in women with premature rupture of membranes.

This study was performed to evaluate the diagnostic performance of maternal serum C-reactive protein, maternal white blood cell (WBC), and neutrophil counts in the detection of histologic chorioamnionitis. One hundred and twenty six pregnant women after at least 28 weeks of gestation with premature rupture of membranes (PROM) were studied. Blood samples for C-reactive protein, WBC and neutrophil counts were taken at delivery.

Platelet storage lesion and apoptosis: are they related?

The relationship between the platelet storage lesion (PSL) and programmed cell death (apoptosis) is poorly understood. Nevertheless, there is some experimental evidence that platelets contain most of the components of the apoptosis machinery and both the apoptotic process and the PSL lead to platelet activation and microvesiculation with expression of phosphatidyl serine (PS) on the outer layer of cell membrane, a hallmark of all nucleated cells. The PS exposure is believed to contribute to the development of inflammatory or immunomodulation process, to the regulation of haemostatic balance and the ultimate clearance of dead or fragmented cells from the circulation.

Leukoreduction of sickle cell trait blood: an unresolved issue.

With the increasing demand for leukoreduction of blood components and the implementation of universal leukoreduction in several countries, the problems associated with leukocyte filtration of sickle cell trait blood have been revisited. Currently, there is no unified standard practice for sickle cell trait donors. Different blood centers adopt different policies.

A case of leucodepletion failure in Cobe spectra plateletpheresis: further studies on the identification of the potential cause.

A 54-year-old double dose donor failed leucodepletion by Cobe LRS for five sequential donations, without triggering the "machine failure alarm". All collections were uneventful but final products appeared lipaemic. The last two donations were studied: (i) by collecting the first half of each donation into one bag and the other half into a second bag.

Studies on the improvement of leucodepletion performance of the Haemonetics MCS+ for production of leucodepleted platelet concentrate.

With the implementation of universal leucodepletion, an in-line, negatively charged LRF6H leucodepleting filter became an essential part of the Haemonetics MCS+ plateletpheresis system. A larger-scale (968) study using the standard protocol revealed a 2.79% leucodepletion failure rate (standard < 5 x 10(6) leucocytes per adult therapeutic dose).

The effect of leucocyte depletion on the quality of fresh-frozen plasma.

The aim of this study was to evaluate the quality of leucodepleted (LD) fresh-frozen plasma (FFP) produced using one of five whole blood filters (Baxter RS2000 & RZ2000, NPBI T2926, Macopharma LST1 and Terumo WBSP) or two plasma filters (Pall LPS1 and Baxter FGR7014). Whole blood or plasma was filtered within 8 h of collection at an ambient temperature. Samples were taken pre- and post filtration for analysis of coagulation factors and complement activation (n = 7--12 for each type of filter).

Platelet storage lesion of WBC-reduced, pooled, buffy coat-derived platelet concentrates prepared in three in-process filter/storage bag combinations.

Background: With the implementation of universal WBC reduction in the United Kingdom, in-process WBC-reduction filters for pooled buffy coat (BC)-derived platelet concentrates (PCs) are used in routine production. The effects of three filter/storage bag combinations on platelet activation and microvesiculation and on the activation of coagulation were investigated.

Study Design And Methods: Using pooled BCs from the same donors, three filter/storage bag combinations (Autostop BC/CLX, Pall Biomedical; Sepacell PLX5/PL2410, Asahi Medical; and Imugard III-PL 4P/Teruflex, Terumo) were compared with unfiltered controls for their effects on microvesiculation and other storage-induced changes in platelets.

Statistical process monitoring of WBC-reduced blood components assessed by two types of software.

Background: Statistical process control is required for monitoring of the WBC-reduction process. This study focused on some factors that may influence the outcomes of statistical process monitoring, such as WBC-reduction technologies, the anticoagulant used, and WBC-counting technologies, by using two types of software.

Study Design And Methods: Data were collected from January to September 1999, before the implementation of universal WBC reduction.