Platelet activation during preparation and storage of concentrates: detection by flow cytometry.

This paper describes a rapid, whole blood micro-method for assessing the activation status of platelets that can be used to monitor changes occurring during the preparation and storage of platelet concentrates. Platelets are examined for the expression of markers of early activation (fibrinogen binding) and of degranulation (GP53 and GMP-140 expression), using flow cytometry. Fibrinogen binding can be detected in a number of blood packs even before processing. Platelet concentrates prepared by the washed platelet method become further activated during centrifugation and separation. More than 90% of platelets in freshly prepared concentrates carried bound fibrinogen (90.9 +/- 7.7%) whilst the GP53 and GMP-140 antigens were expressed on 11.3 +/- 3.3% and 13.7 +/- 5.1 of these cells respectively (mean +/- SD). Fibrinogen binding fell on storage of the platelets for four days, attributed to shedding of the fibrinogen molecule.