The laboratory and the new oral anticoagulants

Measurements of the effect of NOAs are indicated in several situations: (a) patients with adverse events (i.e., thrombotic/hemorrhagic), particularly those who present with overdosage owing to excessive drug intake or decreased clearance; (b) patients undergoing surgical procedures for ensuring that no residual drug remains in the circulation; (c) patients requiring anticoagulation reversal because of life-threatening hemorrhage; (d) patients with renal insufficiency, who are likely to accumulate the drug in the circulation; (e) patients with liver failure, because NOAs are metabolized by the liver; (f) patients taking other drugs that might increase/decrease the effects of NOAs via drug- drug interactions. The choice of tests is based on such characteristics as availability, linearity of the dose- response curve, standardization, and responsiveness to increasing drug dosage. Practitioners need to be aware that NOAs can interfere with the measurement of common hemostasis parameters.