Thrombin generation estimates the anticoagulation effect of direct oral anticoagulants with significant interindividual variability observed

Abstract

: Direct oral anticoagulants (DOACs) are increasingly being used, primarily due to their drug stability and patient convenience. Although these drugs have been evaluated to be well tolerated in numerous clinical trials, their impact on in-vivo anticoagulation effect, variability and therapeutic drug level remains unknown. Hence, we aim to study the effect and variability of DOACs on thrombin generation via the calibrated automated thrombogram. Anonymized coagulation specimens from outpatients on warfarin were collected. Pooled normal plasma samples were spiked with increasing concentrations of dabigatran, rivaroxaban and apixaban. Similarly, plasma samples with normal coagulation profiles were spiked with two concentrations each of dabigatran, rivaroxaban and apixaban. Thrombin generation via calibrated automated thrombogram was run using the above samples and compared with a dataset of normal controls. Increasing international normalized ratio was associated with a reduction of endogenous thrombin potential (ETP) and thrombin peak and increasing lag time. Factor Xa inhibitors produced a flattened thrombin generation curve with a reduction of thrombin peak and relative preservation of ETP. Direct thrombin inhibitors produced a reduction of both ETP and thrombin peak and increasing lag time. Seventy-one citrated plasma samples (26 dabigatran, 21 rivaroxaban and 24 apixaban) were evaluated. The two concentrations produced a reduction of thrombin generation parameters with significant interindividual variability compared with neat plasma of 35-93, 13-31 and 18-71% and for dabigatran, rivaroxaban and apixaban, respectively. Thrombin generation can measure the anticoagulation effect of commonly used DOACs, with each drug having a unique thrombin generation profile. The variability noted using the same concentration suggests significant interindividual pharmacodynamic differences, which maybe relevant with respect to efficacy as well as bleeding side effects. Further delineation of the modifiers of interindividual differences is required in the in-vivo setting.

Assessment of the analytical performances and sample stability on ST Genesia system using the STG‐DrugScreen application

“…Tailoring drug dosages to fit the needs of individual patients could be helpful to make old and new drugs more effective and safer . Preliminary observations showed that thrombin generation testing is affected by all anticoagulant drugs and therefore it could be the candidate assay . The test has been found to be very sensitive to all kind of anticoagulants and may best represent the interindividual response than just exploring plasma drug concentrations .…”

“…Preliminary observations showed that thrombin generation testing is affected by all anticoagulant drugs and therefore it could be the candidate assay . The test has been found to be very sensitive to all kind of anticoagulants and may best represent the interindividual response than just exploring plasma drug concentrations . In addition to considering the interindividual response to an antithrombotic drug, thrombin generation testing is also able to explore in more detail the effect of anticoagulants on the coagulation process.…”

The impact of oral anticoagulants on haemostasis

“…44 Finally, although a therapeutic range has not been established for DOACs, recent studies demonstrate that levels in extreme ranges (too low, or too high, compared to the published "on therapy" levels) are associated with clinical outcomes as bleeding or thrombosis. [45][46][47] Since several studies have found large inter-individual variation in drug levels it could be argued that a functional assay would give additional information on this patient's individual coagulation status.…”

“…The correlation between the different doses of DOACs and measured drug levels is rather weak, reflected by broad "on-therapy" ranges. 50,[52][53][54] Although for some DOACs drug levels are associated with clinical outcome, such as bleeding and thrombosis [45][46][47] , this has not been translated into a clinically useful therapeutic window.…”

“…To overcome this artefact, multiple groups have used donor plasmas in the TG well, and normal pooled plasma (NPP) (without dabigatran) in the calibrator wells. 26,43,46 This method eliminates one of the benefits of CAT-TG: that samples are calibrated with their own plasma. It is known that the colour and the unique composition of plasma will affect the results of TG.…”