Improving the Management of Warfarin May Be Easier Than We Think

Performance variation is easy to find—all one needs to do is to look for it. We have long known that some nations achieve better control of hypertension than others,1 some hospitals have shorter door-to-balloon times than others,2 and some cardiac surgeons have better risk-adjusted mortality after coronary artery bypass graft surgery than others.3 In fact, it is difficult to recall an instance when performance was found not to vary. Given that performance variation is ubiquitous, it is no longer shocking to find it; the more interesting question is why performance varies so much. The answer to this question would likely be a key step along the pathway to improving performance.Article see p 2309It is rather uncommon to find a single answer to the question of why performance variation exists. However, in the current issue of Circulation , Van Spall and colleagues4 have found an unusually straightforward explanation for performance variation, at least in the context of the management of warfarin. The authors found that site-level adherence to a relatively simple algorithm regarding when to change the dose of warfarin and when not to change the dose predicted fully 87% of between-center variance. Adding patient-level clinical variables (ie, risk-adjustment), center-level variables, and country-level variables only increased the amount of explained variation to 89%. In short, management of warfarin doses appeared to be almost deterministic regarding the anticoagulation control that was achieved. Remarkably, the authors also found that greater adherence to the algorithm also predicted a reduced rate of the combined primary end point of stroke, major hemorrhage, or death at the site level. For each 10% increase in algorithm-consistent dosing at the center level, the annual rate of the combined end point was 8% lower, even after adjusting for a host of patient-level predictors. The …