Current Concepts of Coagulation and Fibrinolysis

Abstract

This chapter discusses current understanding of coagulation and fibrinolytic systems, their clinical impact, and variables affecting the laboratory assessment of thrombotic and bleeding disorders. It begins with the introduction about coagulation and fibrinolysis. Then goes on to discuss basic concepts of coagulation—namely, role of platelets, activation of the coagulation cascade, contribution of leukocytes to coagulation, and inhibitors of coagulation. Next the chapter has discussed about basic concepts of fibrinolysis—namely, fibrinolysis activators and fibrinolysis inhibitors. Anticoagulant theory is also discussed in the chapter wherein conventional heparin, low-molecular-weight heparins, oral anticoagulant therapy, thrombin inhibitors, and platelet inhibitors are described. The chapter has also explored clinical aspects and discussed about molecular defects, laboratory assessment of hemostatic activation, antiphospholipid antibodies, and the study of platelet function by flow cytometry. The chapter then turns to the discussion of nonanalytical variable affecting the laboratory evaluation of hemostasis—namely, preanalytical variables affecting global coagulation tests, minimizing in vitro platelet activation and preanalytical variables affecting analysis of fibrinolysis. Strategy for the systematic examination of thrombophilia is also discussed in the chapter. Finally the chapter closes with the conclusion stating that our concepts of coagulation and fibrinolysis are still evolving. The increasing use of molecular methods in the laboratory has uncovered new mutations and has facilitated the understanding of the genetic basis of hemostatic defects.