Introduction to Coagulation

A comprehensive list of coagulation test options can be found in the Hemostasis and Thrombosis Test Compendium. This document can be printed and will serve as a quick reference for ordering the appropriate tests/profiles as needed by the clinician.

The Coagulation Appendix provides a basic overview of hemostasis and thrombosis with particular focus on the role of the clinical laboratory. Hemostasis can be defined as the physiological process that keeps blood flowing while allowing solid clot formation, or thrombosis, to prevent blood loss from sites of vascular damage.^1,2 This requires a delicate balance between a potent coagulation mechanism that rapidly forms a stable clot and a regulatory system that limits clot formation to the site of injury. As the site of damage is repaired, fibrinolysis degrades the clot and restores unrestricted blood flow.

In general, there are four clinical situations that call for the use of coagulation tests in the assessment of patients. These are:

1. Excessive bleeding: Defects in primary and secondary hemostasis are potential causes of excessive bleeding (see Primary Hemostasis and Secondary Hemostasis).

• Abnormal Bleeding Profile (116004)
• Menorrhagia Profile (336572)

2. Increased risk of thrombosis: A number of congenital and acquired conditions can lead to pathologic clot formation (see Thrombophilia).

3. Therapeutic monitoring: More details about tests used to monitor anticoagulant therapy are provided under the following:

• Apixaban (Eliquis®) (117085)
• Dabigatran (Pradaxa®) (117076)
• Factor X, Chromogenic (117904)
• Fondaparinux Anti-Xa (500465)
• Heparin Anti-Xa (117101)
• Partial Thromboplastin Time (PTT), Activated (005207)
• Prothrombin Time (PT) (005199)
• Rivaroxaban (Xarelto®) (117050)

4. Pathologic thrombosis: More details about tests used to evaluate thrombotic conditions are provided under the following:

• D-Dimer (115188)
• Disseminated Intravascular Coagulation (DIC) (116012)
• Disseminated Intravascular Coagulation (DIC) Profile, Comprehensive Plus (117853)
• Heparin-induced Platelet Antibody (150075)

Frozen Gel Packs. To ensure specimen integrity during warm weather, follow these Instructions for Use of frozen gel packs and specimen lockboxes.

References

1. Brandt JT. Overview of hemostasis. In McClatchey KD, ed. Clinical Laboratory Medicine. 2nd ed. Baltimore, Md: Lippincott Williams and Wilkins; 2002:987-1009.

2. Liu MC, Kessler CM. A systemic approach to the bleeding patient. In Kitchens CS, Alving BM, Kessler CM, eds. Consultative Hemostasis and Thrombosis. Philadelphia, Pa: WB Saunders; 2002:181-196.