The direct oral
anticoagulants (DOACs), now including
dabigatran,
apixaban and
rivaroxaban, have given clinicians alternative options to low molecular weight heparins (LMWHs) and
vitamin K antagonist
therapy, including
warfarin, for the treatment of
atrial fibrillation and treatment and prevention of venous thromboembolic (VTE) disease. DOACs have been successfully marketed as not requiring monitoring; however, there will be situations where clinicians will request laboratory testing, including emergency department admissions for haemorrhage or
thrombosis, or emergency surgical interventions. We report the results of several Royal College of Pathologists of Australasia Quality Assurance Programs (RCPAQAP) surveys using
apixaban and
rivaroxaban spiked samples to either assess the suitability of certain potential screening or
drug-quantifying assays, for assessment of
drug presence or absence or measurement of levels, as well as assessing potential interference in a wide variety of haemostasis assays. We also include additional evaluations using ex vivo samples from patients given
apixaban and
rivaroxaban for various therapeutic reasons. The prothrombin time (PT) and activated partial thromboplastin time (APTT) show better sensitivity with
rivaroxaban than
apixaban. Anti-Xa assays show good concordance and reproducibility with expected
drug levels; however, availability of these assays may be limited to larger institutions. Interference of
apixaban and
rivaroxaban on haemostasis testing extends beyond routine coagulation assays to encompass a plethora of specialised assays, including factor assays, lupus inhibitor, and FVIII inhibitor estimation. In conclusion, this report highlights the influence of these drugs on most tests performed in haemostasis laboratories, and the potential for some tests to predict the presence, absence or level of these drugs in plasma.