Ecarin clotting time (ECT) is a laboratory test used to monitor anticoagulation during treatment with

hirudin Hirudin is a naturally occurring peptide in the salivary glands of blood-sucking leeches (such as ''Hirudo medicinalis'') that has a blood anticoagulant property. This is essential for the leeches' habit of feeding on blood, since it keeps a h ...

, an

anticoagulant An anticoagulant, commonly known as a blood thinner, is a chemical substance that prevents or reduces the coagulation of blood, prolonging the clotting time. Some occur naturally in blood-eating animals, such as leeches and mosquitoes, which ...

medication Medication (also called medicament, medicine, pharmaceutical drug, medicinal product, medicinal drug or simply drug) is a drug used to medical diagnosis, diagnose, cure, treat, or preventive medicine, prevent disease. Drug therapy (pharmaco ...

which was originally isolated from

leech Leeches are segmented parasitism, parasitic or Predation, predatory worms that comprise the Class (biology), subclass Hirudinea within the phylum Annelida. They are closely related to the Oligochaeta, oligochaetes, which include the earthwor ...

saliva. Ecarin, the primary reagent in this assay, is derived from the venom of the saw-scaled viper, ''

Echis carinatus ''Echis carinatus'', known as the Sindh saw-scaled viper, saw-scaled viper,Mallow D, Ludwig D, Nilson G (2003). ''True Vipers: Natural History and Toxinology of Old World Vipers''. Malabar, Florida: Krieger Publishing Company. 359 pp. . Indian sa ...

''. In the clinical assay, a known quantity of ecarin is added to the plasma of a patient treated with hirudin. Ecarin activates

prothrombin Prothrombin (coagulation factor II) is encoded in the human by the F2-gene. It is proteolytically cleaved during the clotting process by the prothrombinase enzyme complex to form thrombin. Thrombin (Factor IIa) (, fibrose, thrombase, throm ...

through a specific proteolytic cleavage, which produces meizothrombin, a prothrombin-thrombin intermediate which retains the full molecular weight of prothrombin, but possesses a low level of procoagulant enzymatic activity. Crucially, this activity is inhibited by hirudin and other direct thrombin inhibitors, but not by

heparin Heparin, also known as unfractionated heparin (UFH), is a medication and naturally occurring glycosaminoglycan. Heparin is a blood anticoagulant that increases the activity of antithrombin. It is used in the treatment of myocardial infarction, ...

. The ECT is also unaffected by prior treatment with

warfarin Warfarin, sold under the brand name Coumadin among others. It is used as an anticoagulant, anticoagulant medication. It is commonly used to prevent deep vein thrombosis and pulmonary embolism, and to protect against stroke in people who ha ...

or the presence of phospholipid-dependent anticoagulants, such as

lupus anticoagulant Lupus anticoagulant is an immunoglobulin that binds to phospholipids and proteins associated with the cell membrane. Its name is a partial misnomer, as it is actually a prothrombotic antibody ''in vivo''. The name derives from their properties ''i ...

. Thus, the ECT is prolonged in a specific and linear fashion with increasing concentrations of hirudin. An enhancement of the ECT is the ecarin chromogenic assay (ECA) in which diluted sample is mixed with an excess of purified prothrombin and the generated meizothrombin is measured with a specific chromogenic substrate. This assay shows no interference from prothrombin or fibrinogen in the sample and is suitable for the measurement of all direct thrombin inhibitors.Fabrizio MC. 2001. Use of Ecarin Clotting Time (ECT) with Lepirudin Therapy in Heparin-Induced Thrombocytopenia and Cardiopulmonary Bypass. JECT 33:117–125
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Journal of The American Society of ExtraCorporeal Technology
Accessed 5 June 2007.Textarin/Ecarin Time
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Specialty Laboratories
Accessed 5 June 2007.Lange U, Nowak G, Bucha E. Ecarin chromogenic assay—a new method for quantitative determination of direct thrombin inhibitors like hirudin. Pathophysiol Haemost Thromb. 2003 Jul-2004 Aug;33(4):184-91.

References

Blood tests {{Immunology-stub