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A Practical Guide to Haemostasis


Prothrombinase-induced Clotting Test [PiCT]

Introduction

The Prothrombinase-induced Clotting Test [PiCT] is a Prothrombinase based test that relies upon the use of of an enzyme isolated from the venom of the Russell viper [Daboia russelli] to activate Factor V and has been developed to facilitate the monitoring of the Heparins, the Direct Thrombin and Xa inhibitors.


Principles & Methodology

Patient citrated platelet poor plasma sample is incubated with a defined amount of Factor Xa, phospholipid and a specific activator of Factor V isolated from the venom of the Russell viper. After a 3 minute incubation period at 37C, CaCl2 is added to re-calcify the sample and allow formation of the Prothrombinase complex and the time to clot formation recorded. The formation of the Prothrombinase complex is independent of endogenous Thrombin activation of Factor V as this is achieved by means of the Russell viper venom. 

The Prothrombinase complex converts Prothrombin to Thrombin.  The rate of clot formation is dependent upon Factor IIa and Factor Xa concentrations and these will be affected by the presence of UFH, LMWH and the Direct Thrombin and Xa Inhibitors. 


Reference Ranges

The median PiCT result for normal individuals not on an anticoagulant is 25.3s with a 95% interval of 19.2 - 30.6s.