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Pall T. Onundarson: Questioning the Dogma of VKA Management

Pall T. Onundarson,Edward Lee Carter/LinkedIn

Jul 6, 2026, 11:18

Pall T. Onundarson: Questioning the Dogma of VKA Management

Pall T. Onundarson, Professor Emeritus at Landspitali University Hospital, shared Edward Lee Carter‘s post on LinkedIn:

”Fortunately, there are people such as Edward Lee Carter that are willing to question the dogma in VKA management – and that warfarin management and outcomes can be fiixed…by replacing the old prothrombin time with a more appropriate test.”

Edward Lee Carter, Clinical Pharmacist Practitioner at U.S. Department of Veterans Affairs, shared a post on LinkedIn:

”Did the arrival of DOACs unintentionally end innovation in warfarin management?

That question has been on my mind recently.

Over the past decade, anticoagulation research has understandably focused on DOACs.

They have transformed care for millions of patients and represent one of the greatest advances in cardiovascular medicine.

But while our attention shifted to developing better drugs…

Did we stop trying to make warfarin itself better?

Warfarin hasn’t disappeared.

Millions of patients still depend on it because of:

Mechanical heart valves
Antiphospholipid syndrome
Advanced kidney disease
Cost considerations
Drug interactions
Other clinical situations where it remains the preferred therapy

Yet we continue to monitor it using PT/INR, a test developed nearly a century ago that was never designed specifically to measure warfarin’s pharmacodynamic effect.

That is where the work of Professor Emeritus of Hematology Dr. Pall T. Onundarson, M.D. deserves another look.

His research, together with colleagues studying Fiix-guided monitoring, asked a simple but important question:

If we can improve the way we monitor warfarin, can we improve patient outcomes without changing the drug itself?

The randomized Fiix trial suggested that monitoring Factors II and X while minimizing the influence of Factor VII reduced thromboembolic events without increasing major bleeding.

Subsequent observational studies from Iceland have continued to support that concept, although broader independent validation is still needed before widespread adoption.

Whether Fiix ultimately becomes the future is almost beside the point.

The bigger question is this:

Why did innovation in warfarin monitoring largely slow once DOACs arrived?

Innovation isn’t always inventing a new medication.

Sometimes it’s questioning long-held assumptions.

Sometimes it’s improving the care of patients who still rely on therapies we already have.

As pharmacists, physicians, laboratorians, and researchers, perhaps we should ask ourselves:

Are we comparing DOACs to the best version of warfarin…or simply the version we’ve always used?

I’d love to hear perspectives from clinicians, laboratorians, and researchers.

Is it time to reopen the conversation around warfarin monitoring?”

Pall T. Onundarson: Questioning the Dogma of VKA Management