R. Cardigan

Current methods of assessing platelet function: relevance to transfusion medicine

There are three areas in transfusion medicine where the assessment of platelet function may be informative: (1) To identify platelet dysfunction in donors of platelet components. (2) To assess whether changing processing or storage methodologies has an impact on platelet function in platelet concentrates (PC). (3) To determine which patients require platelet transfusions and whether these platelet transfusions are effective by assessing platelet function in the recipient. Traditionally, platelet function tests are time-consuming to perform, difficult to quality control, lack sensitivity and usually require specialist laboratory support. However, during the last 10 years, significant developments have occurred in this field. Tests that provide more information on global haemostasis, rather than a single facet of platelet function, are now available, and some tests can be applied in a nearpatient manner, rather than by specialized laboratories, so that results can be used to tailor therapy. We do not intend this review to be a ‘shopping list’ of tests that blood services should apply to PC, but aim to review methods for assessing platelet function that we believe might be relevant to transfusion and whether they have been applied in this setting. Platelet enumeration is reviewed elsewhere [1].

Storage of platelets in additive solutions: a multicentre study of the in vitro effects of potassium and magnesium

Background and Objectivesu2002 In a preliminary study, the presence of potassium and magnesium in a modified synthetic medium (PAS‐III) was found to have a significant influence on platelet metabolism (using apheresis‐derived, as well as buffy‐coat‐derived platelets) when compared with standard PAS‐III. The differences included reduced glycolysis, as evidenced by lower consumption of glucose and lower production of lactate, but also better preservation of pH and hypotonic shock response reactivity. The results suggested that storage in modified PAS‐III containing 20% plasma was comparable to storage in standard PAS‐III containing 30% plasma. To confirm the preliminary results and to evaluate the effects of different preparation protocols, an international multicentre study, which included 11 different sites, was conducted.

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 8u2003h of collection at an ambient temperature. Samples were taken pre‐ and post filtration for analysis of coagulation factors and complement activation (nu2003=u20037–12 for each type of filter). All filtered units (209–286u2003ml) contained <u200a5u2003×u2003106 residual leucocytes and <u200a30u2003×u2003109/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.

In vitro function of platelet concentrates prepared after filtration of whole blood or buffy coat pools

Background/methodu2002 Data on the quality of platelet concentrates (PC) produced by the buffy coat method and stored beyond 5 days in plasma are limited. We therefore evaluated the quality of PCs prepared by leucocyte depletion of whole blood (Terumo WBSP, n = 10) or a buffy coat pool (Pall Autostop, n = 10), and stored for 7 days in plasma by assessing platelet parameters and markers of platelet activation.

A simple spectrophotometric method for the quantification of residual haemoglobin in platelet concentrates.

Background and Objectivesu2002 High levels of residual haemoglobin (Hb 0·1 g/l) are known to decrease the efficiency of pathogen‐inactivation systems. We evaluated three separate methods to quantify Hb in platelet concentrates (PC).

The influence of platelet additive solutions on cytokine levels and complement activation in platelet concentrates during storage

Background and Objectives The accumulation of platelet‐derived cytokines in platelet concentrates (PC) during storage may contribute towards non‐haemolytic transfusion reactions (NHTR). We investigated the effect of platelet storage medium on platelet activation, complement activation and cytokine levels in leucocyte‐reduced PC.

Coagulation factor content of plasma produced from whole blood stored for 24 hours at ambient temperature: results from an international multicenter BEST Collaborative study

BACKGROUND: There is increasing international interest in producing components from blood that has been stored at room temperature for 24 hours. The lack of comprehensive data on the quality of plasma produced from blood stored in this way led to this international study.

Interlaboratory comparison of red-cell ATP, 2,3-diphosphoglycerate and haemolysis measurements.

Background and Objectivesu2002 Red blood cell (RBC) storage systems are licensed based on their ability to prevent haemolysis and maintain RBC 24‐h in vivo recovery. Preclinical testing includes measurement of RBC ATP as a surrogate for recovery, 2,3‐diphosphoglycerate (DPG) as a surrogate for oxygen affinity, and free haemoglobin, which is indicative of red cell lysis. The reproducibility of RBC ATP, DPG and haemolysis measurements between centres was investigated.

Platelet concentrates from fresh or overnight‐stored blood, an international study

BACKGROUND: Whole blood and also buffy coats (BCs) can be held for a few hours or overnight before processing into blood components or platelet concentrates (PCs). Individual studies have reported a range of outcomes regarding in vitro variables for PCs prepared from fresh and stored whole blood. In this multicenter study, effects of storage of whole blood or BCs on the in vitro quality of PCs were studied.

Value of central analysis of leucocyte depletion quality control data within the National Blood Service, England

Background and Objectives The results of quality monitoring leucocyte counts were analysed nationally for the first 2 years of universal leucocyte depletion (LD), spanning the time‐period before and after standardization of the counting and LD methods. The objectives were twofold: first to determine whether the implementation strategy was effective in achieving the LD specification (< 5 × 106 leucocytes in 99% of components with 95% statistical confidence); and second, whether quality monitoring was able to detect potential non‐conformance.