Peter Brønnum Nielsen1, Søren Lundbye-Christensen2, Lars Hvilsted Rasmussen3, Torben Bjerregaard Larsen4. 1. Thrombosis Research Unit, Aalborg University, Aalborg, Denmark. Electronic address: pbn@rn.dk. 2. Department of Cardiology, Aalborg AF study group, Aalborg University Hospital, Aalborg, Denmark. 3. Thrombosis Research Unit, Aalborg University, Aalborg, Denmark. 4. Thrombosis Research Unit, Aalborg University, Aalborg, Denmark; Department of Cardiology, Aalborg AF study group, Aalborg University Hospital, Aalborg, Denmark.
Abstract
INTRODUCTION: Warfarin is the most widely prescribed vitamin K antagonist and in the United States and Europe more than 10 million people are currently in long-term oral anticoagulant treatment. This study aims to retrospectively validate a dynamic statistical model providing dosage suggestions to patients in warfarin treatment. MATERIALS AND METHODS: The model was validated on a cohort of 553 patients with a mean TTR of 83%. Patients in the cohort were self-monitoring and managed by a highly specialised anticoagulation clinic. The predictive model essentially consists of three parts handling INR history, warfarin dosage and biological noise, which allows for prediction of future INR values and optimal warfarin dose to stay on INR target. Further, the model is based on parameters initially being set to population values and gradually individualised during monitoring of patients. PRIMARY OUTCOME: Time in therapeutic range was used as surrogate quality measure of the treatment, and model-suggested dosage of warfarin was used to assess the accuracy of the model performance. RESULTS: The accuracy of the model predictions measured as median absolute error was 0.53 mg/day (interquartile range from 0.25 to 1.0). The model performance was evaluated by the difference between observed and predicted warfarin intake in the preceding week of an INR measurement. In more than 70% of the cases where INR measurements were outside the therapeutic range, the model suggested a more reasonable dose than the observed intake. CONCLUSION: Applying the proposed dosing algorithm can potentially further increase the time in INR target range beyond 83%.
INTRODUCTION:Warfarin is the most widely prescribed vitamin K antagonist and in the United States and Europe more than 10 million people are currently in long-term oral anticoagulant treatment. This study aims to retrospectively validate a dynamic statistical model providing dosage suggestions to patients in warfarin treatment. MATERIALS AND METHODS: The model was validated on a cohort of 553 patients with a mean TTR of 83%. Patients in the cohort were self-monitoring and managed by a highly specialised anticoagulation clinic. The predictive model essentially consists of three parts handling INR history, warfarin dosage and biological noise, which allows for prediction of future INR values and optimal warfarin dose to stay on INR target. Further, the model is based on parameters initially being set to population values and gradually individualised during monitoring of patients. PRIMARY OUTCOME: Time in therapeutic range was used as surrogate quality measure of the treatment, and model-suggested dosage of warfarin was used to assess the accuracy of the model performance. RESULTS: The accuracy of the model predictions measured as median absolute error was 0.53 mg/day (interquartile range from 0.25 to 1.0). The model performance was evaluated by the difference between observed and predicted warfarin intake in the preceding week of an INR measurement. In more than 70% of the cases where INR measurements were outside the therapeutic range, the model suggested a more reasonable dose than the observed intake. CONCLUSION: Applying the proposed dosing algorithm can potentially further increase the time in INR target range beyond 83%.