Abstract
The introduction of the new oral direct anticoagulants dabigatran, rivaroxaban and apixaban within the past few years has changed clinical practice as these drugs do not need routine laboratory testing compared to the traditional vitamin K antagonists. However, in specific clinical situations such as invasive emergency procedures, severe haemorrhage or deteriorating renal function measurement of the anticoagulatory effect may be required. The effects of the intake of an oral direct inhibitor on readily available qualitative laboratory tests such as prothrombin time (PT), activated partial thromboplastin time (aPPT) and thrombin time (TT) depend on which oral direct inhibitor the patient has taken, the dose and the time the drug was last taken and the sensitivity of the test reagents. A quantitative determination of the Xa-inhibitors rivaroxaban and apixaban plasma concentration is possible using a specifically calibrated anti-factor Xa assay. The diluted thrombin time test (Hemoclot) is useful for measuring the plasma concentration of the thrombin inhibitor dabigatran. When interpreting global coagulation tests of patients on direct oral inhibitors one should be aware that these new anticoagulants can affect screening and diagnostic clotting tests.
A good communication between clinicious and other laboratory is necessary to deal with the various effects of DOACs on coagulation assay.
