Laboratory coagulation tests in patients treated by direct oral anticoagulants (DOACs)

Routine clotting time assays (Prothrombin Time/INR, activated Partial Thromboplastin Time [aPTT]) are prolonged at variable extent by direct oral anticoagulants (DOAC), according to the assay, the reagent and the type of DOAC. These assays are not reliable for monitoring the intensity of treatment and the measurement of the plasma level of the DOAC is usually not required. At high concentrations, DOAC interfere with the routine clotting assays, making them difficult to interpret. In critical situations such as major bleeding or urgent invasive procedure, the measurement of DOAC level and its kinetics are simple and useful to manage the patient.