Biological Variation of Hemostasis Analytes in Atrial Fibrillation Patients Using Dabigatran

Background: Analytical criteria for laboratory analysis based on biological variation are considered state-of-theart. While biological variance should ideally be measured in patient populations for whom the tests are relevant, data are mostly only available from healthy individuals. We determined the biological variance of activated partial thromboplasmin time (APTT), prothrombin time (PT), fibrinogen, and trough dabigatran levels in patients with atrial fibrillation (AF) who were treated with dabigatran. Methods: Between 2019 and 2022, patients with AF treated > 3 months with dabigatran were included. Blood was collected monthly up to 10 times for the measurement of APTT, PT, fibrinogen, and trough dabigatran levels. Between-subject variance (CVG), within-subject variance (CVI), and analytical variance (CVA) were calculated. Results: Eighteen participants (median age 65.8 years, 22.2% women) were included, with 130 samples in total. For APTT, the CVG was 11.5%, the CVI 8.8%, and the CVA 1.1%. For PT, these values were 5.2%, 4.0%, and 1.0% and for fibrinogen 13.6%, 11.8%, and 1.6%, respectively. For the dabigatran levels, the percentages were 37.9%, 33.0%, and 3.4%, respectively. Conclusions: We assessed the biological variance of APTT, PT, fibrinogen, and dabigatran in a patient population with long-term dabigatran use. The analytical performances of coagulation laboratory tests in patients with AF treated with dabigatran were comparable to those in healthy volunteers.