Effect of previous INR control during VKA therapy on subsequent DOAC adherence and persistence, in patients switched from VKA to DOAC.

Introduction Current guideline suggests a switch from vitamin K antagonist (VKA) to direct oral anticoagulant (DOAC) in patients with low time in therapeutic range (TTR<70%). Poor INR control may be the result of poor compliance, and might therefore be associated with subsequent DOAC intake. Therefore, this study evaluates the effect of previous TTR and other measures of INR control on DOAC non-adherence and non-persistence, in patients who switched from VKA to DOAC. Methods 437 patients who switched from VKA to DOAC between 2012 and 2019 were included using data from Certe Thrombosis Service, IADB.nl pharmacy community database University Groningen and Statistics Netherlands. DOAC prescriptions were used to determine non-adherence and non-persistence. INR control (i.e. TTR, time under therapeutic range (TUR) and INR variability) was assessed during the last 180 days of VKA use. Multivariable regression models were applied to determine the association between INR control and DOAC non-persistence / non-adherence. Results On VKA, 67.7% of the patients had a TTR below 70%. DOAC non-persistence was 39.8% (95% CI 33.4-45.5%) during a median follow-up of 34.4 months [IQR 19.1-49.2]. Approximately 80% of persistent patients were DOAC-adherent. Low TTR was not associated with DOAC non-persistence (HR 1.14, 95% CI 0.69-1.87) and DOAC non-adherence (OR 1.38, 95% CI 0.67-2.84), nor were TUR and INR variability. Conclusion Previous INR control during VKA therapy is not associated with subsequent DOAC non-adherence and non-persistence. This study suggests that INR control on VKA cannot, and therefore should not be used for predicting DOAC adherence or persistence.