Pall Torfi Onundarson
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, www.hartbio.co.uk.