M. J. George1, C. Cox1, K. Aroom1, T. Sharma1, M. Skibber1, B. Gill1 1The Univeristy Of Texas Health Science Center At Houston,Department Of Surgery,Houstn, TX, USA
Introduction: Various devices exist capable of detecting platelet activity and an effect of antiplatelet therapy. However, these devices only offer qualitative data without basis in direct measurement of platelet activity. There is no existing clinical assay capable of quantitatively detecting platelet contractile forces. The purpose of this study is to create a novel assay to detect anti-platelet drug effects on clotting by measuring contractile forces of platelets in clotting whole blood.
Methods: After appropriate IRB approval whole blood samples were collected from healthy human subjects before and after taking 325 mg of oral aspirin. Calcium chloride was added to citrated samples to initiate clotting. Samples were placed in a temperature controlled glass test chamber with acrylic inserts of matched surface areas at the top and bottom creating a cylindrical blood sample of known height and radius. A camera recorded deflection of a bent wire attached to the top acrylic insert. Using beam equations, force generated by the contracting clot was recorded with time. Kinetic metrics such as clot activation, rate of contraction and clot volume change are recorded. Student t-tests compared metrics taken from the force curves.
Results: Qualitative analysis of force curves identified an activation phase prior to a clot reaching a steady state rate of contraction. Student t-tests comparing rates of steady state clot contraction demonstrated aspirinated blood contracted slower, thus generated force at a slower rate than control blood (20.24 versus 23.92 micro-Newtons per second, p = 0.032). Time to reach steady state contraction also was longer for aspirinated blood compared to control blood (588 versus 435 seconds, p = 0.043).
Conclusion: This novel blood coagulation assay detects force generated by platelets in a contracting clot with time and demonstrates the kinetics of blood clotting. Aspirinated blood develops force at a slower rate and takes more time to reach a steady state of contraction than control blood.
