M. Beard

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

The aim of this study was to evaluate the quality of leucodepleted (LD) fresh‐frozen plasma (FFP) produced using one of five whole blood filters (Baxter RS2000 & RZ2000, NPBI T2926, Macopharma LST1 and Terumo WBSP) or two plasma filters (Pall LPS1 and Baxter FGR7014). Whole blood or plasma was filtered within 8 h of collection at an ambient temperature. Samples were taken pre‐ and post filtration for analysis of coagulation factors and complement activation (n = 7–12 for each type of filter). All filtered units (209–286 ml) contained < 5 × 106 residual leucocytes and < 30 × 109/l platelets. Statistically significant losses of factors V, VIII, IX, XI and XII and increases in markers of coagulation activation were observed (0–21%), which were dependent on filter type. None of the filters had a significant effect on von Willebrand factor (VWF) multimeric distribution or the activity of VWF and factors II, VII or X. The effect on levels of C3a appeared to be related to the filter surface charge: positively charged filters resulted in C3a generation, whereas negatively charged resulted in C3a removal. None of the observed changes are likely to be clinically significant unless subsequent processing of plasma (such as pathogen inactivation) results in further losses of coagulation factors.

Blood components produced from whole blood using the Atreus processing system.

BACKGROUND: The Atreus 2C+ system (Gambro BCT) automates whole blood (WB) processing into a single device. This study compared the quality of red blood cells (RBCs), fresh‐frozen plasma (FFP), and buffy coats (BCs) made from WB held with or without active cooling.

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.

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 2 10 6 leucocytes per adult therapeutic dose). Factors influencing the efficacy of the filter were investigated. The pH of the filtrate was 7.0, the temperature 28°C and filtration rate 80 ml/min. Reduction of the filtration rate to 30 ml/min (784 doses) reduced leucodepletion failure to 0.38%. Measurement of the leucocyte count, pre- and post-filtration of the platelet products, revealed that donations from 1% of donors contained substantially larger numbers of leucocytes in pre-filter samples (300-1500/ w l) than in control samples (35-70/ w l). This number tends to increase progressively with subsequent donations in these individuals, leading to leucodepletion failure, whilst peripheral leucocyte counts remain normal. The new continuous filtration protocol (version C) using a less impact filter LRF-XL and a lower (7 ml/min) head pressure was also effective but failure still occurred twice on one of the donors who persistently showed high pre-filter count. We conclude that leucodepletion failures in the Haemonetics system are related to both donor leucocyte (i.e., being light and non-adherent) and operational/filter performance.

The role of in process qualification in quality improvement of the haemonetics MCS plus leucodepleted platelet concentrate

With the implementation of universal leucodepletion in UK all leucodepletion processes have gone through a standard process qualification and quality improvement. The Haemonetics MCS system is a well established automated platelet collection system for the production of double dose leucoreduced platelet concentrate (WBC approximately 70x10(6)/dose). Recently an automated post collection filtration harness system has been introduced (MCS plus LDP) in which platelets are filtered, using an in-line PALL polyester filter (LRFH6 PALL) to reduce the WBC level to below 5x10(6) WBC/dose. This system passed our Phase I evaluation process based on 20-40 runs. However, some changes in the final volume of the products were needed to conform to national guidelines. Large scale trials using the new volume adjusted protocol revealed occasional failure in the leucocyte content. Therefore, 100% testing had to be implemented on all products. A national evaluation was carried out to determine whether changing the filter to a more efficacious one, the LRFXL (PALL) or slowing the filtration flow rate can influence the overall outcome. To reduce donor variability, known donor population were used with identical apheresis conditions. A more consistent and systematic drop in leucocyte content was observed by reducing the flow rate whereas a similar failure (i.e. 1-3%) rate was found both in controls and LRFXL when using the standard head pressure, which is recommended by the manufacturer. A similar failure rate was found using three different low leucocyte counting technologies (Nageotte, flow cytometry and Imagn 2000). It is recommended that a process qualification/validation program should be implemented when even a small modification in the collection system is introduced.

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. Those from platelet and plasma filters were mainly lymphocyte with considerable differences depending on the type of leucodepletion process. Atypical leucocytes are often seen in some pre-/post-cellular leucofiltered components. These appear characteristically as small WBC with a lower affinity for filter matrix, or as cell fragment, pinched leucocyte or apoptotic cells. Different reagents in use show variable sensitivity in identifying these extra gatal events. Storage of leucodepleted samples also induces different types of abnormality in leucocyte dot plot. A useful practical approach for characterisation of the nature of leucocyte sub-populations causing failure in leucodepleted components is provided.

YS05 In Vitro Evaluation of Platelet Concentrates Prepared Using the Automated Gambro OrbiSac System

Introduction  The Gambro OrbiSac device is designed to automate the preparation of platelet concentrates (PC) from buffy coats (BC). The aim of this study was to evaluate the in vitro function of PC produced using the OrbiSac system and stored in plasma.

P04 In Vitro Evaluation of Buffy Coat Derived Platelet Concentrates in SSP+ Platelet Storage Medium

Introduction  As part of the process to improve the safety and quality of the platelet supply, the NBS is evaluating the use of platelet storage media (PSM). The objective of this study was to produce a platelet concentrate (PC) containing 70% SSP+ and 30% plasma, whilst maintaining platelet yield, and to evaluate their in vitro function. Study Design. Buffy coats were prepared using the standard NBS method and four (ABO matched) were pooled together with 250 mL of SSP+. Centrifugation was performed using optimised conditions for PSM and an Optipress used to express the PC through a Pall Autostop LD filter into a Pall ELX storage bag. Ten PCs were prepared, and platelet quality was assessed using in vitro assays for functionality and activation on days 1, 5, 7 and 9 of storage.