Variation in activation marker expression within the platelet population – a new parameter for evaluation of platelet flow cytometry data

Abstract

In flow cytometry, individual cells are investigated. Platelet activation is normally reported in form of percentage of platelets expressing the marker (positive platelets) and/or mean/median fluorescence intensity (MFI) for the entire analyzed population. None of these take into account the variance of the marker expression between individual platelets. This can be obtained as data on coefficient of variation (CV). This study explores if CV provides additional information regarding platelet function. Samples from platelet concentrates (PCs) prepared by apheresis- (n = 13) and interim platelet unit (IPU) technique (n = 26) and stored for 6–7 days were included and compared. Spontaneous- and agonist-induced expression of activation markers (fibrinogen binding and exposure of P-selectin, LAMP-1, and CD63) was investigated as percentage positive platelets, MFI and CV. Spontaneous expression of P-selectin as percentage positive platelets and MFI was higher for IPU PCs than apheresis PCs, which in contrast had higher agonist-induced activation. CV for spontaneous fibrinogen binding and P-selectin exposure was larger for apheresis PCs, while IPU PCs generally had larger CV for P-selectin, LAMP-1, and CD63 after agonist stimulation. Our findings show that CV adds additional information when assessing platelet activation by providing data on the variation in activation responses within the platelet population.

Keywords:

• Blood platelets
• coefficient of variation
• CV
• flow cytometry
• platelet activation

Acknowledgements

The authors wish to thank Maria Wallstedt and Anna Södergren for their contributions in the setup of the study and practical analysis of the samples and Helena Lindblom and Ana Maria Vasilache for arrangements surrounding sample collection.

Author contributions

SR and NT designed and supervised the study. FM analyzed the data and wrote the initial draft of the manuscript and AA re-worked it for submission with a new focus. All authors took part in the revision and editing of the final version of the manuscript, and have read and agreed to the final version.

Data availability statement

The raw data used for this publication can be provided by the authors upon reasonable request.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This research was funded by ALF Grants, Region Östergötland, grants from Region Östergötland, and strategic research grants from Örebro University.