The Myth of the Stable INR Patient

Some medical experts have contested that patients treated with warfarin with stable INR values might not benefit from being switched to one of the novel oral anticoagulants.

However, they do believe it’s imperative to maintaining INR values in the 2.0-3.0 range for the safety and efficacy of warfarin.

Sean Pokorney, MD, MBA and his colleagues used the US ORBIT AF registry to analyze chronic INR management of 3,749 atrial fibrillation (AF) patients treated with warfarin with at least 9 INR measurements during an 18-month period of follow up across 144 sites.

A prime analysis was conducted at 6 months, which calculated the proportion of INR values in the 2.0-3.0 range 6 months prior and 12 months following the landmark.

Researchers found only 10% to have 100% of their INR values in the therapeutic range, while 26% of patients had 80% or more in therapeutic range.

Over the next 12 months, nearly 90% and 92% of these 2 definitions of “stable INR patients” experienced at least one INR measurement outside of the 2.0-3.0 range.

Only 10% of patients who were administered chronic warfarin experienced full INR values in therapeutic range within the 6-month period, and 90% of those patients are expected to go through minimum one INR value beyond therapeutic range.

As such, research due to be presented Saturday, March 14 at the American College of Cardiology Annual Scientific Sessions indicated only few patients are actually stable on warfarin. Furthermore, a past record of stability can only provide weak predictions of future results.