Rivaroxaban and Apixaban Anti-Xa Measurements: Impact of Plasma Storage for 7 Days at Room Temperature

The advent of direct oral anticoagulants (DOACs) is a major breakthrough in the management of patients with venous thromboembolic diseases and atrial fibrillation. Clinical trials with DOACs have been performed without laboratory assessment, owing to their predictable anticoagulant response and wide therapeutic index. However, there are several circumstances in which assessment of DOAC effect may be desirable.[1] [2] [3] [4] Besides life-threatening situations in which an assay with rapid turnaround time may impact patient care, in settings such as extreme body weight, renal function impairment, gastrointestinal malabsorption, drug interactions or suspicion of overdose, a non-urgent measurement of DOAC may be needed.[1] [2] [3] [4] Only specific tests are deemed reliable to accurately measure DOAC concentrations but they are not widely available on a 24h/7d basis. Therefore, in non-urgent situations, samples may be transferred to a central laboratory and testing may be delayed for cost and workflow efficiency. To ensure precise and accurate measurements, both inappropriate storage conditions and the expiration of a time-limit before assaying the sample should be avoided. Nevertheless, precise data about storage conditions and maximum time before assaying the sample are lacking.