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 fundamental for the leeches’ habit of feeding on blood, since it keeps a h ...
, an
anticoagulant
Anticoagulants, commonly known as blood thinners, are chemical substances that prevent or reduce coagulation of blood, prolonging the clotting time. Some of them occur naturally in blood-eating animals such as leeches and mosquitoes, where the ...
medication
A medication (also called medicament, medicine, pharmaceutical drug, medicinal drug or simply drug) is a drug used to diagnose, cure, treat, or prevent disease. Drug therapy (pharmacotherapy) is an important part of the medical field and re ...
which was originally isolated from
leech
Leeches are segmented parasitic or predatory worms that comprise the subclass Hirudinea within the phylum Annelida. They are closely related to the oligochaetes, which include the earthworm, and like them have soft, muscular segmented bodie ...
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 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 saw-scaled viper, little I ...
''.
In the clinical assay, a known quantity of
ecarin is added to the plasma of a patient treated with hirudin. Ecarin activates
prothrombin
Thrombin (, ''fibrinogenase'', ''thrombase'', ''thrombofort'', ''topical'', ''thrombin-C'', ''tropostasin'', ''activated blood-coagulation factor II'', ''blood-coagulation factor IIa'', ''factor IIa'', ''E thrombin'', ''beta-thrombin'', ''gamma- ...
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. Since heparins depend on the activity of antithrombin, they are considered anticoagulants. Specifically it is also used in the treatm ...
. The ECT is also unaffected by prior treatment with
warfarin
Warfarin, sold under the brand name Coumadin among others, is a medication that is used as an anticoagulant (blood thinner). It is commonly used to prevent blood clots such as deep vein thrombosis and pulmonary embolism, and to prevent strok ...
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''. Lupus anticoagulant in living systems cause ...
. 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]
PDF
a
Journal of The American Society of ExtraCorporeal Technology
Accessed 5 June 2007.[Textarin/Ecarin Time](_blank)
at
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
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