A practical approach to disorders of hemostasis.

Simple screening tests are available to detect abnormalities in the plasma coagulation system and platelet function. Prothrombin time reflects the integrity of the extrinsic system, while activated partial thromboplastin time indicates whether the intrinsic system is intact. Thrombin clotting time is a measure of the integrity of the end stage of clotting. Prothrombin time is also helpful in monitoring warfarin therapy; either of the latter two tests can perform a similar function in patients receiving heparin. Ivy bleeding time is the best screening test of platelet function. If bleeding time is prolonged but results of plasma coagulation tests are normal, specialized platelet function tests may be necessary.