FXaIs (rivaroxaban, apixaban, and edoxaban) laboratory evaluation
| Tests/assays . | Suggested indications and interpretations . |
|---|---|
| PT | Perform Stat |
| On therapy—variably prolonged depending on the sensitivity of PT reagent | |
| Above on therapy—often prolonged | |
| Normal PT—does not rule out clinically relevant* drug level | |
| aPTT | On therapy—usually unaffected |
| Above on therapy—may be prolonged | |
| Thrombin time | Unaffected in any scenario |
| Drug-specific calibrated anti-Xa–based assay = nanograms per milliliter | Often not offered Stat |
| Measure accurate FXaI concentration | |
| Useful for compliance or failed therapy | |
| Scheduled major or critical surgery | |
| Heparin assay expressing anti-Xa activity = international units per milliliter | Can be performed Stat because of liquid reagent with longer onboard stability |
| Useful to rule out clinically relevant drug levels to avoid use of reversal/hemostatic agent |
| Tests/assays . | Suggested indications and interpretations . |
|---|---|
| PT | Perform Stat |
| On therapy—variably prolonged depending on the sensitivity of PT reagent | |
| Above on therapy—often prolonged | |
| Normal PT—does not rule out clinically relevant* drug level | |
| aPTT | On therapy—usually unaffected |
| Above on therapy—may be prolonged | |
| Thrombin time | Unaffected in any scenario |
| Drug-specific calibrated anti-Xa–based assay = nanograms per milliliter | Often not offered Stat |
| Measure accurate FXaI concentration | |
| Useful for compliance or failed therapy | |
| Scheduled major or critical surgery | |
| Heparin assay expressing anti-Xa activity = international units per milliliter | Can be performed Stat because of liquid reagent with longer onboard stability |
| Useful to rule out clinically relevant drug levels to avoid use of reversal/hemostatic agent |
Level is <75 ng/mL for bleeding and <50 to 30 ng/mL for urgent surgery.7,8