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08-08-2011 | Cardiology | Article

Warfarin treatment in AF ‘varies significantly’ across practices


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MedWire News: Warfarin treatment in patients with atrial fibrillation (AF) is suboptimal and varies significantly across practices, study findings suggest.

Paul Chan (University of Missouri, Kansas City, USA) and co-authors examined contemporary warfarin treatment rates in AF patients before the expected introduction of newer anticoagulants, as well as the extent of practice-level variation in warfarin treatment.

The study, published in the American Journal of Cardiology, included 9113 AF outpatients from 20 practice sites within the National Cardiovascular Data Registry (NCDR) Practice Innovation and Clinical Excellence (PINNACLE) program. All the patients were at moderate-to-high risk for stroke (defined as a congestive heart failure/hypertension/age/diabetes/stroke [CHADS2] score >1) and would be optimally treated with warfarin.

The team used hierarchical models to quantify the extent of site-level variation with the median rate ratio (RR), interpreted as the likelihood that two random practices would differ in treating identical patients with warfarin.

The findings revealed that overall, only 55.1% of the patients were treated with warfarin. Untreated patients and treated patients were similar in terms of CHADS2 score, age, congestive heart failure rate, hypertension, diabetes mellitus, and previous stroke, "suggesting an almost random pattern of treatment," report the authors.

However, at the practice level, there was significant variation in warfarin treatment, ranging from 25% to 80%, with a median RR of 1.31 (p<0.001).

"This suggests moderate site-level variation in warfarin treatment across practices," say Chan and team.

Furthermore, multivariate analysis demonstrated that the median RR for practice-level variation explained a larger amount of the observed variance in warfarin treatment than any other patient characteristic.

"Our findings therefore suggest that warfarin treatment will remain suboptimal unless characteristics of high-performing practices can be identified and generalized to those practices with the lowest rates," write the authors.

The presence of substantial site-level variation reflects differences in the quality of care among practices, they add.

Chan and team conclude: "Our findings suggest important opportunities for practice-level improvement in stroke prevention for outpatients with AF and define a benchmark treatment rate before the introduction of newer anticoagulation agents."

MedWire ( is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2011

By Piriya Mahendra

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