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AIM OF THE STUDY
To better appreciate the role of the non-vitamin K oral anticoagulants (NOACs) for patients with non-valvular atrial fibrillation in Switzerland we aimed to assess the quality of vitamin K antagonist (VKA) anticoagulation in daily practice.

METHODS
In a cross-sectional study, clinically stable patients on VKA treatment for non-valvular atrial fibrillation for at least 6 months, documentation of international normalised ratio (INR) values for at least 3 months and with at least two INR values were included. The percentage of INR values within the therapeutic range of 2.0 to 3.0 and the time in therapeutic range (TTR; Rosendaal method) and predictors for these measures of VKA anticoagulation quality were assessed.

RESULTS
We studied 332 patients (62% male, mean age 74 ± 9 years) with median (interquartile range) CHA2DS2Vasc and HAS-BLED scores of 4 (3-5) and 3 (2-4) points. The median number of INR values per patient was 8 (5-14), and the average interval between INR measurements was 20 (13-27) days. The percentage of INR values between 2.0 and 3.0 was 67% (50-83%). The median TTR was 69% (51-89%), and TTR ≥65% was found in 202 (61%) patients. Independent predictors of ≥80% INR values between 2.0 and 3.0 included a longer interval between INR measurements and the non-use of spironolactone. The non-use of amiodarone and spironolactone and a longer interval between INR measurements were the only independent predictors of a TTR ≥65%.

CONCLUSIONS
The quality of VKA anticoagulation in Switzerland is highly variable. Importantly, only 60% of patients achieve a TTR ≥65%, which is currently considered to be the minimal acceptable TTR required for VKA therapy. There are few clinical predictors of a good VKA anticoagulation quality. These data may represent a novel basis for decision making regarding the choice of anticoagulation for atrial fibrillation in Switzerland.