Method for monitoring anticoagulant therapy

Abstract

A method of measuring the combined activity of both and only coagulation factors II and X for the purpose of monitoring anticoagulant therapy, and kits for using the method. This is based on the hypothesis that the combined activity of factor II and factor X (FII and FX) more accurately reflects clottability and the antithrombotic effect of VKA anticoagulants in patients than conventional methods (eg PT, P&P). The method involves mixing of test plasma from a human to be tested with specially prepared plasma deficient in both and only coagulation factors II and X but with normal levels of other factors (referred to herein as Fiix-deficient plasma or Fiix plasma), in order to correct for any possible deficiency in other coagulation factors than FII and FX in the test sample. By adding a coagulation reagent and calcium, the generation of thrombin or fibrin can be measured. Kits of the invention comprise a coagulation reagent, calcium and specially made plasma that is deficient in both and only factor II and factor FX. The kit components are suitably lyophilised.

1 . A method for measuring the activity of an anticoagulant drug in a patient, which is based on measuring in a test plasma sample from said patient combined activity of only coagulation factors II and X, the method comprising:
 mixing said test plasma sample with plasma deficient in only factor II and factor X,   adding to said test plasma sample one or more coagulation reagent and calcium, and   determining blood clotting ability by measuring blood clotting time or thrombin generation.   
     
     
         2 . The method of  claim 1 , wherein said anticoagulant drug is vitamin K antagonist. 
     
     
         3 . The method of  claim 1 , wherein the ratio of said test plasma sample and said deficient plasma is in the range from 1:1 to 1:20. 
     
     
         4 . The method of  claim 1 , wherein said one or more coagulation reagent is selected from the group consisting of:
 i) thromboplastin,   ii) phospholipids,   iii) factor IXa,   iv) factor XIa,   v) factor XIIa,   vi) kallikrein,   vii) exogenous activator, including snake venoms that activate factor X, and   viii) factor VIIa.   
     
     
         5 . The method of  claim 4 , comprising adding a contact activator selected from the group consisting of
 i) kaolin particles,   ii) celite,   iii) glass particles,   iv) silica particles, and   v) ellagic acid.   
     
     
         6 . The method of any  claim 1 , further comprising the step of diluting said test plasma sample with buffer or saline solution. 
     
     
         7 . The method of  claim 1 , wherein said coagulation reagent is diluted with water, a saline aqueous solution or buffered aqueous solution. 
     
     
         8 . The method of  claim 1 , wherein at least one component of said coagulation reagent, deficient plasma or calcium source is lyophilised, and wherein the method further comprises a step of reconstituting said at least one component. 
     
     
         9 . The method of  claim 1 , wherein the step of determining blood clotting ability comprises a method selected from the group consisting of:
 manual/visual coagulation detection,   mechanical and/or electronic methods for observing viscosity changes,   optical methods of detecting clot formation,   chromogenic detection using chromogenic substrates,   fluorogenic detection using fluorogenic substrates, and   luminogenic detection.   
     
     
         10 . A test kit for measuring the activity of an anticoagulant drug in a patient, comprising:
 a coagulation reagent, and   normal plasma that is deficient in factor II and factor X and which contains other factors including factor VII and IX (Fiix deficient plasma).   
     
     
         11 . The test kit according to  claim 10  comprising in one container said coagulation reagent and said Fiix deficient plasma. 
     
     
         12 . The test kit of  claim 10  comprising a source of calcium ions. 
     
     
         13 . The test kit according to  claim 10  comprising a first container comprising said coagulation reagent and said Fiix deficient plasma. 
     
     
         14 . The test kit of  claim 10  comprising in a first container said coagulation reagent and in a second container said Fiix deficient plasma. 
     
     
         15 . The test kit according to  claim 10 , wherein said coagulation reagent is selected from one or more of
 i) thromboplastin,   ii) phospholipids,   iii) factor IXa,   iv) factor XIa,   v) factor XIIa,   vi) kallikrein,   vii) exogenous activator, including snake venoms that active factor X, and   viii) factor VIIa.   
     
     
         16 . The test kit according to  claim 15 , wherein said coagulation reagent comprises phospholipids, wherein the kit comprises in one container said coagulation reagent, a contact activator as described in  claim 4 , and Fiix deficient plasma. 
     
     
         17 . The test kit according to  claim 16 , wherein said coagulation reagent and/or said Fiix deficient plasma is lyophilized.