Mandy Hubbard¹, Cale Burge², Geoff Kershaw²

¹NSWHP Coffs Harbour Base Hospital; 2 NSWHP Royal Prince Alfred

When patients taking direct Xa inhibitors Apixaban or Rivaroxaban are switched to UFH or LMWH the disappearance of the DOAC sometimes needs to be measured. This study aimed to validate a plasma heparin neutralisation procedure that allows accurate measurement of apixaban and rivaroxaban during the bridging period.

Samples from healthy volunteers, as well as excess plasma from patients treated with Apixaban/Rivaroxaban/UFH/LMWH were double spun and frozen at ≤40ºC before testing. Normal donor plasma and plasma from patients receiving DOACs were spiked with UFH/LMWH then treated with Hepzyme® (Siemens) then re-tested for apixaban, rivaroxaban, UFH and LMWH. Scenarios assessed:

1.     UFH and clexane spiked into normal plasma to assess the degree of false apixaban/rivaroxaban levels, followed by reversal with Hepzyme.

2.     Spiking of UFH/LMWH to 0.5 and 1.0IU/mL into plasma containing apixaban or rivaroxaban to assess degree of DOAC overestimation relative to baseline, followed by treatment with Hepzyme and re-assaying of apixaban/rivaroxaban to compare baseline levels.

Accurate measurement of apixaban and rivaroxaban is possible using Hepzyme to remove UFH or LMWH when it is concurrently present in test plasma. This may have benefits in an urgent pre-surgical setting.