Dabigatran tests correlate closely with dabigatran levels measured by the reference standard method, LC/MS. The dTT, ecarin tests, and anti-IIa assay are the tests of choice to measure the plasma concentrations of dabigatran. Results must be expressed by interpolating the clotting time or chromogenic activity from a calibration curve locally constructed by testing certified calibrators at increasing dabigatran concentrations.
When the dilute thrombin time (dTT) is used with a drug calibrator, there is a robust linear relationship between dabigatran levels across a wide range of concentrations with less accuracy at or above 500 ng/mL.
Apixaban, Edoxaban, or Rivaroxaban tests and anti-factor Xa assays should measure the plasma concentrations of these three drugs. Chromogenic assay methods allow for direct determination of the substrate's activity. Determining anticoagulants' inhibiting activity on factor Xa is one of the most traditional chromogenic substrate methods. In this assay, activation of factor X in the sample is induced with one factor X–activating enzyme. The activated factor is directly detected with a chromogenic substrate. Undetectable anti-FXa activity probably excludes clinically relevant drug concentrations.
