Role of platelet age in assessment of coagulation.

There are two important reasons why most platelet function studies can be inaccurate. First, platelet function deteriorates when blood is taken out of the vascular tree. Second, tests performed on platelets removed from the blood do not incorporate the role of other cellular and chemical components that may alter platelet activity. This article demonstrates that a coagulation test developed in our laboratory can accurately assess the role of platelet age on the speed of the coagulation of blood. Samples (5.0 mL) of citrated venous blood from 15 volunteers were divided into two groups. One group (n = 6), comprised of subgroups A, B, C, and D of 950 microL aliquots each, was tested within 3 hours. The second group (n = 9), comprised of subgroups E, F, G, and H of 950 microL aliquots each, was tested at 24 hours. The aliquots were added to 50 microL saline without collagen (subgroups A and E), 50 microL saline with 10 micrograms collagen (subgroups B and F), 50 microL saline with 50 micrograms collagen (subgroups C and G), and 50 microL saline with 100 micrograms collagen (subgroups D and H). All collagen-incubated fresh blood samples were significantly more hypercoagulable (shorter recalcification times) compared with the control (no collagen) blood. In the 24-hour-old blood, changes were significant only in the sample with 50 micrograms/mL collagen. We conclude that these data authenticate the role of platelet age in the assessment of the coagulation process.