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Improved warfarin  anticoagulation control with the Fiix-test

Do you want to reduce thromboembolism in your patients by 50-60% in the long-term?

We believe that it is now time to "fiix" warfarin and other VKA management by starting to monitor the right effect of warfarin. This can be achieved by replacing the PT/INR with a new monitoring test,

the Fiix-test.

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Anticoagulation Monitoring

Our scientific work and that of others´ suggest that a suboptimal test has been used for seven decades to monitor

warfarin and other vitamin K antagonists (VKAs). The research suggests that the traditional monitoring test, the prothrombin time (PT or PT/INR), is a partial cause of suboptimal clinical outcome of patients treated with these drugs over decades.


We concluded that only the influence of factors II and X should be monitored. Therefore, we designed a new test, the Fiix-test that only reflects the activity of factors II and X. Hence, it is called "Fiix" test or Fiix prothrombin time (Fiix-PT), the name referring both to factors ii and x - and to fixing the monitoring method.


Two clinical studies have shown that replacing traditional INR monitoring with the Fiix normalized ratio stabilises the anticoagulant effect, reduces the number of tests needed, reduces dose adjustment need and reduces thromboembolism by 50-60% and even more in the long-term.  The improved antithrombotic effect is obtained without causing increased bleeding.

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Visual abstract (1).tif

Blood (2021) 137 (20): 2745–2755.


Warfarin and other VKAs have been monitored for 70 years with the prothrombin time; the PT or PT-INR. All this time their main problem has been variable anticoagulation which has mainly been blamed on food and drug interactions with warfarin.  The PT, invented in 1935, measures the influence of reductions in three (out of four) vitamin K dependent coagulation factors, namely factors II, VII and X. In patients treated with VKAs such as warfarin, over the years it was felt to be needed to reduce all vitamin K dependent factors. ​


However, in vitro and animal experiments suggest that  mainly reductions in factors II and X are relevant to the VKA antithrombotic effect. Moreover, factor VII has a much shorter half-life than factors II and X. Hence, reduced factor VII has major short-term influence on the PT and the INR when little changes have occurred in factors II and X. Therefore, fast occurring reductions in factor VII lead to INR prolongations that are irrelevant to the true anticoagulation state in the patient. The consequence of this is too frequent testing and too frequent as well as imprecise dose adjustments

- and our research shows that this leads to suboptimal clinical efficacy.

In short, the sensitivity of the PT to reduced factor VII confounds the management of these drugs

and causes suboptimal clinical outcome with VKAs. 


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