Performance of Various Laboratory Assays in the Measurement of Dabigatran in Patients Receiving Therapeutic Doses

OBJECTIVES: To study dabigatran etexilate, a new oral anticoagulant that functions as a direct thrombin inhibitor. METHODS: This study evaluates four methods, one of which is performed in three different laboratories, and compares results against dabigatran levels measured by Boehringer-Ingelheim (Ingelheim, Germany) using mass spectrometry. RESULTS: Although routine monitoring is not required, measurement of plasma concentrations may be necessary in certain clinical situations. Routine coagulation assays such as the prothrombin time, activated partial thromboplastin time, and thrombin time do not reliably determine levels of dabigatran anticoagulation. Alternative assays, when calibrated with a dabigatran standard, such as the modified dilute thrombin time, ecarin clotting time, and ecarin chromogenic assay, may be appropriate, although a comparison of these methods using samples from patients taking dabigatran has not been performed. CONCLUSIONS: Although results using all methods in this study demonstrate adequate correlation, measured dabigatran levels varied in a statistically significant manner, even when the same method was used by different laboratories. The clinical significance of this variation in dabigatran concentrations is uncertain.