A guide for diagnosis of patients with arterial and venous thrombosis.

Inasmuch as coagulation laboratories are involved in providing a diagnosis for underlying causes of venous and arterial thrombosis, we present a comprehensive review of the biological properties and functions of the components of the hemostatic system as they relate to the diagnosis of arterial and venous thrombosis. Moreover, as coagulation laboratories are necessary to evaluate the success of initial treatment modalities and to provide guidance for supplemental therapeutic intervention, we include information on antiplatelet and antithrombotic therapy. Included in clinical coagulation testing are assays that evaluate the potential of blood to form clots and tests for platelet numbers and platelet functions. Clot-based assays directly detect the biological activity of procoagulant factors and fibrinogen; chromogenic substrate assays evaluate proteolytic activities of clotting as well as fibrinolysis enzymes; and specific antibodies measure the concentrations of coagulation and fibrinolysis enzymes in plasma. Genetic testing is rapidly becoming incorporated into the clinical routine. The prothrombin time (PT), activated partial prothrombin time (APTT), and thrombin time (TT) are screening assays that measure the clotting times of recalcified whole blood or platelet-poor plasma. In addition to their function as screening assays, PT, APTT, and TT are the backbone of all the specialized clot-based assays for factor activities and for the indirect measurement of inhibitory antithrombin and protein C activities. Molecular markers related to hemostasis and fibrinolysis consist of proteins or peptides that indicate an ongoing physiological or abnormal process related to clot formation, thrombosis, vascular damage, or drug effect. Molecular markers are currently identified by means of specific antibodies prepared against them. The list of hemostatic molecular markers is rapidly growing. Most of the assays developed for molecular marker measurement, with the notable exception of the d-dimer assay, are typically used in clinical research.