Modified plasma-based ecarin clotting time assay for monitoring of recombinant hirudin during cardiac surgery

Tak Shun Choi, Adil I. Khan, Philip E. Greilich, Martin H. Kroll

Research output: Contribution to journalArticlepeer-review

10 Scopus citations


Recombinant hirudin (r-hirudin) is being used increasingly for therapeutic anticoagulation in patients with heparin-induced thrombocytopenia undergoing cardiovascular surgery. Although multiple laboratory methods are available for measuring r-hirudin, the ecarin clotting time (ECT) is the most commonly used for this purpose. Ecarin (extracted from snake venom) converts prothrombin to meizothrombin, which promotes clot formation. Direct thrombin inhibitors, like r-hirudin, bind meizothrombin and yield a linear, dose-dependent prolongation of ECT. Low levels of prothrombin and fibrinogen in plasma samples can lead to higher ECT, suggesting falsely elevated r-hirudin levels. A modified ECT assay with prothrombin and fibrinogen in excess was, optimized using an orthogonal array method to eliminate the variations in patients' plasma prothrombin and/or fibrinogen levels for accurate determinations of plasma r-hirudin levels. By using the modified ECT assay, falsely elevated r-hirudin levels can be avoided in patients undergoing cardiopulmonary bypass, thus providing reliable and accurate r-hirudin monitoring in this clinical setting.

Original languageEnglish (US)
Pages (from-to)290-295
Number of pages6
JournalAmerican journal of clinical pathology
Issue number2
StatePublished - Feb 2006


  • Cardiac surgery
  • Ecarin clotting time
  • Linear regression
  • Plasma-based
  • r-hirudin

ASJC Scopus subject areas

  • Pathology and Forensic Medicine


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