Background:
Direct oral anticoagulants (DOACs) are known to interfere with thrombophilia assays such as lupus anticoagulant (LA), antithrombin (AT), protein C, protein S and activated protein C resistance. The impact of DOACs on result interpretation can cause misdiagnosis and clinical consequence. Interruption of anticoagulation for the purpose of thrombophilia testing exposes patients to an increased risk of thrombosis.
Aim:
Evaluation of DOAC-Stop® (Haematex Research, Australia) to eliminate the interference of DOACs on thrombophilia assays.
Method:
48 DOAC treated (12 dabigatran, 23 rivaroxaban and 13 apixaban) LA negative patients, 56 LA positive patients, 42 LA positive patients spiked with DOACs and 33 normal controls were enrolled. AT activity (HemosIL® - Liquid Antithrombin), dRVVT screen and confirm (HemosIL® - dRVVT Screen and Confirm), APTT (HemosIL® - SynthASil) and plasma concentrations of DOACs (HemosIL® - Liquid Anti-Xa) were assayed on the ACL TOP CTS 500 analyser (Instrumentation Laboratory). The pre and post DOAC-Stop® procedure results were compared using a paired t-test.
Results:
A significant decrease in dabigatran, rivaroxaban and apixaban plasma concentrations was observed in DOAC treated patients following the DOAC-Stop® procedure (251.4 to 2.6 ng/mL (p = 0.004), 223.9 to 4.1 ng/mL (p < 0.0001) and 255.6 to 2.2 ng/mL (p < 0.0001) respectively). Similar results were observed in LA positive patients spiked with dabigatran, rivaroxaban, apixaban and edoxaban (350.1 to 1.3 ng/mL (p = 0.02), 395.4 to 3.5 ng/mL (p = 0.01), 388.3 to 1.7 ng/mL (p = 0.02) and 361.9 to 3.1 ng/mL (p = 0.005) respectively). Prior to the DOAC-Stop® procedure, false positive results for LA assays were observed in all DOAC treated patients. Following the DOAC-Stop® procedure all DOAC treated patient’s results were negative for LA assays. Following the DOAC-Stop® procedure, LA positive patients spiked with DOACs remained positive for all LA assays. A significant overestimation of AT was observed in all direct Xa inhibitor treated and spiked patients following the DOAC-Stop® procedure. There was no significant difference in LA positive and normal control patients following the DOAC-Stop® procedure.
Conclusion:
The DOAC-Stop® procedure is effective at eliminating DOAC interference on thrombophilia assays to allow the accurate interpretation of results in patients receiving DOAC therapy.