Hemostasia

Laboratory Evaluation of Hemostasis
Roger S. Riley, M.D., Ph.D., Ann R. Tidwell, MT(ASCP) SH, David Williams, M.D., Ph.D., Arthur P. Bode, Ph.D., Marcus E. Carr, M.D., Ph.D.

Table of Contents
Table of Contents
CBC/Platelet Count/Blood Smear Examination ________________________ In Vivo Evaluation of Primary Hemostasis _____________________________ Platelet Aggregometry_____________________________________________ Automated Platelet Function Analysis ________________________________ Platelet Aggregation with Impedance Platelet Counting _________ Platelet Aggregation Under Flow Condition ____________________ Acceleration of Kaolin Activated Clotting Time by
Platelet-Activating Factor ________________________________ Automated Optical Platelet Aggregometry Whole BloodHemostatometry ______________________________________ Thromboelastography _____________________________________ Clot Retraction ___________________________________________ Clot-Based Assays _______________________________________________ Activated Clotting Time (ACT) ______________________________ Prothrombin Time (PT) _____________________________________ Activated Partial Thromboplastin Time_______________________ Thrombin Time ___________________________________________ Clotting Factor Assays ____________________________________ Fibrinogen Analysis _______________________________________ Plasma Mixing Studies ___________________________________ Reptilase Time __________________________________________ Dilute Russell Viper Venom Assay __________________________ Activated Protein C Resistance____________________________ Chromogenic Analysis ___________________________________________ Latex Agglutination/Turbidimetry __________________________________ Enzyme Immunoassay ___________________________________________ Flow Cytometry _________________________________________________ Electrophoresis _________________________________________________ Genetic and Molecular Assays____________________________________ Electron Microscopy _____________________________________________ Radioimmunoassay ______________________________________________ References ______________________________________________________ 4 4 6 8 8 8 9 9 10 10 11 11 12 13 13 14 14 15 16 16 17 17 18 18 19 20 20 22 22 22

Hemostasis

Introduction
Medical evaluation of the hemostasis system began with visual observationof the clotting process. During the time of medical blood letting, observation of the size of the clot in a basin (clot retraction) was used to determine when blood letting had to be decreased. In the early 20th century, manual timing of whole blood clotting (i.e., Lee-White Whole Blood Clotting Time), and later plasma, in glass tubes permitted a more accurate measurement of blood clotting. Furtherdiscoveries about hemostasis in the 1930’s and 1940’s led to more sophisticated laboratory tests, including the prothrombin time, activated partial thromboplastin time, and specific assays of platelet function and fibrinolysis. The advent of the monoclonal antibody, molecular analysis, and the microcomputer in the 1980s led to an explosion of knowledge about hemostasis and hemostasis testing thatis still growing. In the hemostasis laboratory, automated assays have replaced many of the manual procedure of the past, and there is increasing interest in rapid, point of care hemostasis assays for perioperative and critical care, as well as self-testing to support the millions of patients now receiving oral anticoagulation for hypercoagulable diseases. Interestingly, measurement of clotretraction is still the focus of a variety of these techniques, a fact that would no doubt be appreciated by the early physicians. This paper presents a global overview of the techniques presently used in the hemostasis laboratory, with the realization that many of these may be quickly surpassed by new information, developments, and applications in the near future.

Laboratory Evaluation of...