Table 2. Indications for laboratory measurement of direct-acting oral anticoagulants (DOACs)2,33,34,36-38.

Clinical indication	Examples of clinical scenarios	Comment about DOAC measurement
Emergency scenarios requiring normal haemostasis	• To assess the utility of an anticoagulant antidote during an acute life-threatening bleeding event • To assess the safety of proceeding with an urgent surgical procedure with high bleeding risk • Pre-thrombolytic therapy assessment for acute stroke	Drug concentration assays:     For all DOACs, drug concentration assays provide a precise gauge. A concentration below 30 micrograms/L may be used for proceeding with invasive procedures. Coagulation function assays:     For apixaban and rivaroxaban, coagulation function assays are not recommended because of insufficient sensitivity to anticoagulant effect.     For dabigatran, the coagulation function assay TCT has excellent sensitivity, and a result within normal reference range is consistent with absence of clinically significant dabigatran concentrations. APTT and PT are not useful.
Scenarios suggestive of excessive DOAC exposure	• Haemorrhagic event • Suspected overdose • Severe acute kidney injury • Concomitant medicines that inhibit CYP3A enzyme or P-glycoprotein transporter	Drug concentration assays:     Measure drug concentration and consult local laboratory or an anticoagulation expert for interpretation of results. Coagulation function assays:     Coagulation function assays are difficult to interpret to provide a gauge of DOAC exposure.
Scenarios suggestive of inadequate DOAC exposure	• Thrombotic event • Malabsorptive gastrointestinal conditions • Concomitant medicines that induce CYP3A enzyme or P-glycoprotein transporter	As per Scenarios suggestive of excessive DOAC exposure

APTT = activated partial thromboplastin time; CYP = cytochrome P450; PT = prothrombin time; TCT = thrombin clotting time