Direct Oral Anticoagulants Concentration Testing in Clinical Practice for High-Risk Patients with AF

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Aim: The aim of this study was to analyse the necessary of coagulation tests for AF patients with high cardiovascular risk in clinical practice.

Design and methods: Quantitative, analytic, cross-sectional clinical study, during the period from April 2018 to February 2019, was performed at Pauls Stradins Clinical University Hospital, Cardiology Centre of Latvia. Data were collected on patients with non-valvular AF on anticoagulation therapy for ≥3 months, defined as a high-risk group by CHA22-VASc score. Concentration was measured using anti-Xa assay and indirect thrombin inhibitors assay. Data were analysed using SPSS.

Results: Data were collected on seven patients, of whom 85.7% (n=6) were men; the mean age was 66.3 (SD ± 5.77) years. The mean CHA22-VASc score was 2.86 (SD ± 1.57). The most common comorbidities were arterial hypertension and coronary artery disease (42.86%; n=3), stroke (42.86%; n=3) and diabetes (28.57%; n=2). Rivaroxaban was used by 71.43% of patients. The increased risk of possible drug–drug interactions most frequently occurred with statins (71.43%; n=5), proton pump inhibitors and anti-inflammatory drugs (42.86%; n=3). Two-thirds of the patients were taking ≥1 drug with potential pharmacokinetics interactions increasing the risk of bleeding. The average Cmax drug concentration in blood was lower than expected, reaching 216.28 ng/ml and decreasing about 67.17% within 24 hours.

Conclusion: Rivaroxaban measurements varied from 27 to 407 ng/ml (median value 143.64 ng/ml) within 24 hours. Three patients had higher than expected rivaroxaban levels.