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Traditional anticoagulation in atrial fibrillation (AF) saves lifes and prevents disability. This was proven years ago. I write this because further improvements can be made.

The results of the meta-analysis of Hart and collegues (1999) were a 62% reduction in stroke in non-valvular atrial fibrillation with PT-monitored warfarin (PT-warfarin) compared to placebo (no anticoagulation).

Ever since, anticoagulation has been standard of care in patients with AF. A meta-analysis of Ruff and collegues (2015) suggested a similar ischemic stroke rate with DOACs and PT-warfarin but less risk of rare intracranial bleeding in AF patients. Therefore, as well as due to their convenience, the DOACs are now recommended over PT-warfarin by most. However, for some patients traditional PT-warfarin is the better choice.

But what about the newer Fiix-test (Fiix-NR) monitored warfarin?

Our two clinical studies of the new and more accurate monitoring method of warfarin found a 36-62% reduction in ischemic strokes in AF-patients with Fiix-test monitored warfarin (Fiix-warfarin) compared to well managed PT-monitored warfarin controls (standard warfarin INR care). Even more during longer-term management. The time in range in our studies was high, about 78-80%. We are hoping to have results of a clinical real-world study comparing PT-warfarin, Fiix-warfarin and DOACs out later in the year 2022.

We think that traditional PT-warfarin instability is partly due to the effect of FVII being monitored with the PT-INR system. The antithrombotic effect is caused by reduced FII and FX, not reduced FVII. Why should we monitor a redundant confounding factor? We therefore hypothesized that ignoring factor VII during warfarin monitoring would improve the stability and effectiveness of the old drug, warfarin. Our clinical studies suggest that this is indeed the case.

Based on the available data sofar, we have concluded that "Fiix-warfarin" is a better/more effective anticoagulant than "PT-warfarin" (ie old fashioned PT-INR monitored warfarin). Fiix-warfarin is also "less inconvenient" as fewer tests and dose adjustments are needed.

Notably, despite increased effectiveness in preventing blood clots with Fiix-NR monitored warfarin, bleeding was not increased with Fiix-warfarin and even possibly decreased but not statistically significantly so.

Because Fiix-warfarin appears to be much more effective than PT-warfarin I simply cannot see one reason to continue monitoring vulnerable patients with a suboptimal test, the old PT-INR. Indeed, we have been monitoring all our patients with the new Fiix-NR since 2016. The nurses (dosing staff) tell me it is much easier to manage Fiix-warfarin than PT-warfarin due to a more stable effect.

We think our warfarin patients deserve the best possible care and we believe that the Fiix test is a part of that, namely Fiix-warfarin.

The Fiix test is obtained from Hart Biologicals in Hartlepool, England,

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The answer is yes. Because the Fiix-PT improves the effectiveness of warfarin markedly without reducing safety. See the publications list for the arguments behind this statement.

The cost of drugs for heart disease in the UK has increased 9-fold between 2014 to 2020, mainly due to switch from warfarin to DOAC drugs (see ).

The DOACs have similar effectiveness as traditionally monitored warfarin but cause somewhat less intracranial bleeding albeit fortunately rarely. But DOAC treatment is much more expensive, even when clinic visits and monitoring costs of VKAs are included.

As the effectiveness of warfarin is improved using the new monitoring method (Fiix-PT based Fiix-NR), should societies consider changing guidelines back in favor of warfarin over DOACs? Or at least in favor of replacing PT-INR monitoring of VKAs with the more effective monitoring method?

We contend that if PT-INR monitoring og VKAs would be replaced by Fiix-NR, patient outcome and convenience would be improved - and that this would save taxpayer´s money and health insurance premiums. Less thromboembolism, less permanent paralysis, reduced disability. The mony could then be better spent elsewhere (or taxes and premiums reduced).

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  • Writer's pictureBrynja Gudmundsdottir

A new warfarin initiation protocol for safe Fiix dose management. J Thromb Thrombolysis

A review article on anticoagulant monitoring: Oral anticoagulant monitoring: Are we on the right track? Int J Laboratory Hematology

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