Abstract
Due to their widespread use, testing for direct oral anticoagulants (DOACs) has become
urgent in certain clinical situations. Screening based on widely available, rapid,
and simple hemostasis assays such as prothrombin time, activated partial thromboplastin
time, or even diluted Russel Viper venom time may provide sufficient evidence of “over-coagulation”
and could be used “in small/peripheral/spoke laboratories” as an emergency strategy,
but is not thought to be reliable for driving clinical decision making. Given their
good correlation with plasma concentration, urine dipsticks may be considered a valuable
alternative for emergency screening, although their performance is dependent on renal
function, may vary depending on the time since the last urination, and there may be
problems of interfacing with the laboratory/hospital information system. Separation
methods based on liquid chromatography and mass spectrometry may be clinically questionable,
since they measure the concentration rather than the actual inhibitory effect of DOACs,
are relatively expensive, cumbersome and time consuming, and therefore seem unsuitable
for most conditions requiring urgent clinical decision making. A proposed approach
therefore involves establishing a network of routine clinical laboratories, designating
a reference center where DOAC tests could be available 24/7, establishing a clear
diagnostic care pathway for ordering the tests from the laboratory and standard operating
procedures for performing them, the use of the diluted thrombin time for dabigatran
and anti-FXa assays (drug-calibrated) for rivaroxaban, apixaban, and edoxaban, as
well as providing expert advice throughout the testing process, from ordering to interpretation
of results.
Keywords anticoagulants - direct oral anticoagulants - measurement - assays
