Table 4. Role of various coagulation assays in detection of the anticoagulant effect of NOACs.
| Coagulation assay | Dabigatran | Rivaroxaban | Apixaban | Comments |
|---|---|---|---|---|
| PT | Lacks sensitivity to detect therapeutic levels, prolonged with supratherapeutic levels | Linear concentration-response curve over a broad range but marked variability between PT reagents | Prolonged, but poor correlation with apixaban concentration Dilute prothrombin time (dPT) may be used to increase sensitivity of standard PT§ |
Can be considered to exclude the supratherapeutic levels of dabigatran Normal PT can be used to exclude the anticoagulant effect of rivaroxaban Not recommended to assess the effects of apixaban |
| aPTT | More sensitive than PT to anticoagulant effect, however the dose-response relationship is lost at concentrations >200 ng/mL | Curvilinear dose-response; poor correlation particularly with higher drug concentration | Concentration-response plateaus after 200 ng/mL, limits utility as drug levels increase | Might be useful to detect supratherapeutic levels of dabigatran Inferior than PT to assess the effect of rivaroxaban Not recommended to assess the effects of apixaban |
| TT | Correlates well with the dabigatran concentration* Normal levels suggest either absence or minimal plasma levels of dabigatran |
Not affected | Not affected | Might be used a screening tool to exclude the anticoagulant effect of dabigatran |
| ACT | Follows a flatter dose-response curve, limited utility | Limited data | Limited data | Might offer quantitative benefit over the use of aPTT for dabigatran, but clinical data remain limited |
| Chromogenic FXa assay | Not applicable | Offers benefit of quantitative estimation of rivaroxaban | Linear to exponential concentration-response | Could be used in conjunction with PT to estimate the effect of FXa inhibitors |
§, dilution of prothrombin time achieved by diluting the thromboplastin reagent in 100 mmol of CaCl2; *, the use of TT assay depends on the coagulometer and also on the reagent (thrombin) used for measurement. NOACs, novel oral anticoagulants; PT, prothrombin time; aPTT, activated partial thromboplastin time; TT, thrombin time; ACT, activated clotting time.