Function of Platelets Used for Transfusions

Overview

Cytotoxic treatment for malignant hematologic disorders often casue thrombocytopenia that can result in life threatening bleedings. This is prevented by platelet transfusions but these can cause serious transfusion reactions and thus the number of transused platelet concentrates should be limited. It is therefore important that the platelet concentrates contain functional platelets with long circulation time in the bloodstream. We have developed a method with flow cytometry to measure platelet function markers. It allows us to determine which pathways that are initiated upon activation. The aim of this project is to assess to what degree spontaneous activation of platelets as well as their activation capacity affects the transfusion response (i.e. uptake in the circulation and circulation time) in the recipient. The hypothesis is that transfusion of platelets with low spontaneous activation and high activation capacity will lead to a higher transfusion response in the recipient.

Cytotoxic treatment for malignant hematologic disorders often casue thrombocytopenia that can result in life threatening bleedings. This is prevented by platelet transfusions but these can cause serious transfusion reactions and thus the number of transused platelet concentrates should be limited. It is therefore important that the platelet concentrates contain functional platelets with long circulation time in the bloodstream. The role of platelets in hemostasis is complex. Upon vascular injury, platelets adhere at the injured site where they become activated, release their granule content and aggregate. Activation include changes in receptors, expression of activation markers and become procaoagulant. We have developed a method with flow cytometry to measures these platelet function markers. It allows us to determine which pathways that are initiated upon activation. Platelets can be stored a maximum of 5-7 days before transfusion. However, the preparation process and subsequent storage can result in platelet lesions, affecting their ability to promote hemostasis and circulate after transfusion. The aim of this project is to assess to what degree spontaneous activation of platelets as well as their activation capacity affects the transfusion response (i.e. uptake in the circulation and circulation time) in the recipient. The hypothesis is that transfusion of platelets with low spontaneous activation and high activation capacity will lead to a higher transfusion response in the recipient. We will be able to examine how this relates to platelet processing methods and storage duration. Platelets will be transfused on normal indications to participants at the hematology ward. The platelet concentrates choosen to be transfused will be done according to regular routines at the blood center. We will thus not control what concentrates are transfused (i.e. preparation method and storage time) and hence included in the study. A small sample will be taken from the platelet concentrate shortly before transfusion and platelet function analysed with the flow cytometry method. Transfusion response will be assessed in the participant by calculation of corrected count increment (CCI) which relates the increase in platelet concentration after transfusion to the number of platelets transfused and the blood volume. CCI is calculated at 1 and 24-hours after transfusion. Clincial variables that might affect the transfusion response such as infection and fever will be registered as well as bleeding. The number of days to next platelet transfusion will be followed up.