Clinical experience with measuring apixaban exposure in Australia

Apixaban is one of the non-vitamin K antagonist oral anticoagulants (NOACs) currently reimbursed on the Australian Pharmaceutical Benefits Scheme (PBS) for stroke prevention in patients with non-valvular atrial fibrillation and >=1 risk factors for stroke. Following reimbursement in September 2013, healthcare professionals have expressed concern regarding the perceived inability to accurately measure apixaban levels. Research use only apixaban-specific calibrators and controls became available in Australia and New Zealand in October 2013, for use with STA-liquid anti-Xa reagent (Diagnostica Stago). During the 8 months following the availability of this apixaban-specific assay, 51 sets of apixaban controls and 38 sets of apixaban calibrators were purchased by laboratories across Australia. This survey investigated the nature and pattern of use of the apixaban-specific assay throughout Australia during this time to determine the frequency of assay use, reasons for measuring apixaban levels in patients, frequency of urgent requests, average assay turnaround times and expected apixaban plasma concentrations.