P01
Use of the DiaMed Impact R to Test Platelet Function in Stored Platelet Concentrates

Authors: Morrison, A.; Hornsey, V.; Macgregor, I.

Source: Transfusion Medicine, Volume 16, Supplement 1, October 2006 , pp. 25-25(1)

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Abstract:

Aim

The DiaMed Impact R tests platelet function under close to physiological flow conditions using cone and plate technology. A blood sample is applied to a polystyrene well and plasma proteins (eg VWF and fibrinogen) adhere to the well surface. Shear force is applied to produce arterial flow conditions leading to adhesion and aggregation of platelets via interaction of various platelet membrane glycoproteins including GPIbα and GPIIb/IIIa with vWF and fibrinogen on the well surface. The adhered platelets are quantified by an image analyser and results expressed as % well surface covered by aggregates (SC %) as an index of adhesion and average size of the aggregates (AS μm²) as an index of aggregation. The machine is designed to use whole blood and we found in preliminary studies that adhesion and aggregation do not occur when platelet concentrates (PCs) are used instead. The aim of this study was to add red cells back to PCs so that function could be studied and changes during storage followed and compared with those observed in our established in vitro assays. Method

ABO compatible routine leucoreduced red cells in SAGM (1 mL) were mixed with 0.6 mL PC to give a final Hct of 35% and platelet count of 400 × 10⁶ mL^-1. These are conditions seen in whole blood except for the reduced levels of leucocytes. Red cells diluted with platelet poor plasma were used as negative controls. The shear rate and time of activation were varied and conditions optimised. Routine PCs were then tested on days 2 and 7. Samples were also stored at 4 °C or 37 °C for 1 to 2 h before assay to see if function could be improved. Results

Optimum conditions of 1800 s^-1 and 4 min activation produced normal values of SC >7.5% and AS >25 μm² Mean values ± SD are shown below. Conclusions

Red cells are required as well as plasma proteins for platelet adhesion and aggregation to be measurable in the Diamed Impact R. Platelet functions of adhesion and aggregation were shown to decrease during storage but improved at 37°C. The decreases seen were similar to those observed in GPIbα and GPIIb/IIIa binding sites, HSR, ESC and swirl.

Document Type: Research article

DOI: http://dx.doi.org/10.1111/j.1365-3148.2006.00694_1.x

Publication date: 2006-10-01