DOACs: role of anti-Xa and drug level monitoring

Direct oral anticoagulants (DOACs) do not require routine monitoring of anticoagulant effect, but measuring DOAC activity may be desirable in specific circumstances to detect whether clinically significant DOAC levels are present (eg, prior to urgent surgery) or to assess whether drug levels are excessively high or excessively low in at-risk patients (eg, after malabsorptive gastrointestinal surgery). Routine coagulation tests, including the international normalized ratio (INR) or activated partial thromboplastin time (aPTT), cannot accurately quantify drug levels but may provide a qualitative assessment of DOAC activity when considering the estimated time to drug clearance based on timing of last drug ingestion and renal and hepatic function. Drug-specific chromogenic and clot-based assays can quantify drug levels but they are not universally available and do not have established therapeutic ranges. In this review, we discuss our approach to measuring DOAC drug levels, including patient selection, interpretation of coagulation testing, and how measurement may inform clinical decision-making in specific scenarios.