Announcement
Thank you for attending THSNA 2026. The virtual meeting is now closed.
Thank you for attending THSNA 2026. The virtual meeting is now closed.
Presentation Details
| Validation of Anticoagulant Neutralizing Agents for Lupus Anticoagulant Testing: Combined Evaluation of DOAC-Stop and Hepzyme �(THSNA �Elizabeth Van Cott Travel Awardee) Gordon Minaker1, Steven Wong2, 3, Hamish Nicolson2, 3. 1Department of Internal Medicine, University of British Columbia, Vancouver, BC, Canada.2Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC, Canada.3Providence Health Care, St.Paul’s Hospital, Vancouver, BC, Canada |
Abstract
Background Lupus anticoagulant (LA) testing is susceptible to analytical interference from anticoagulant medication; however, it is often impractical to discontinue anticoagulant therapy prior to testing. We performed analytical and clinical validation of DOAC-Stop (activated charcoal) and Hepzyme (bacterial heparinase) for removing direct oral anticoagulants (DOACs) and unfractionated heparin (UFH) during LA testing. Objectives Validate use of DOAC-Stop and Hepzyme on control and patient samples to (1) neutralize DOAC- and UFH-related LA assay interference, (2) preserve true LA detection, and (3) perform reliably in patient specimens submitted for LA testing while receiving anticoagulants. Methods Testing was performed using HemosIL reagents on an ACL TOP 750 (Werfen) in two phases: (1) analytical validation using four LA-negative and two LA-positive plasmas tested neat, after anticoagulant spiking, and post-neutralization; and (2) prospective evaluation of clinical specimens from patients receiving apixaban (n=70), rivaroxaban (n=6), or UFH (n=19). Testing included PT/INR, aPTT, TT, anti-Xa and dRVVT/SCT screen/confirm, and normalized ratio (NR). Spiking studies used apixaban/rivaroxaban (125, 250, 500 ng/mL) and UFH (0.2, 2.0 IU/mL). LA cutoffs were dRVVT NR >1.23 and SCT NR >1.29. Results Analytical Validation Neither DOAC-Stop nor Hepzyme altered clotting times or LA interpretations in drug-free plasmas. Apixaban caused disproportionate prolongation of the dRVVT confirm, producing downward shift of NRs (Fig.1); LA-negative mean NR decreased from 0.99→0.70 (-29%) and LA-positive mean NR decreased from 1.70→1.54 (−9%). SCT effects were minimal. No false-positive/negative dRVVT or SCT results observed. DOAC-Stop restored all results to baseline. Rivaroxaban caused disproportionate prolongation of the dRVVT screen, producing a strong, dose-dependent upward shift of NRs (Fig.1); LA-negative mean NR increased from 0.99→1.38 (+39%) with false-positive NRs in 1/4, 3/4, and 4/4 LA-negative plasmas at 125, 250, and 500 ng/mL. LA-positive mean increased from 1.70→2.68 (+58%). SCT effects were minimal. DOAC-Stop corrected all interference. UFH caused minimal changes at 0.2 IU/mL, but 2.0 IU/mL produced marked dRVVT NR elevation (Fig.1); LA-negative mean NR increased from 0.99→1.46 (+47%) with 4/4 false-positive NRs and one false-positive SCT NR. Hepzyme corrected all interference. Prospective Clinical Evaluation Average apixaban level was 160 ng/mL pre and 3.0 ng/mL post-DOAC-Stop. DOAC-Stop corrected one false-positive and eight false-negative dRVVT NRs (11%), confirming apixaban’s LA-masking effect (Fig.2). After neutralization, 40% remained LA-positive (dRVVT). Average rivaroxaban level was 144 ng/mL pre and 0.2 ng/mL post-DOAC-Stop. DOAC-Stop corrected three false-positive dRVVT NRs (50%), demonstrating rivaroxaban induced LA-mimicry (Fig.2). After neutralization, 50% remained LA-positive (dRVVT). Average UFH level was 0.68 IU/mL pre and 0.08 IU/mL post-Hepzyme. Hepzyme corrected four false-positive dRVVT NRs (21%), demonstrating UFH-induced LA mimicry (Fig.2). After neutralization, one sample remained positive (dRVVT). SCT showed no NR misclassification in any of the anticoagulated patients. Discussion/Conclusion Analytical and clinical data showed that apixaban can mask LA (false-negative dRVVT NRs), while rivaroxaban and UFH can mimic LA (false-positive dRVVT/SCT NRs). DOAC-Stop and Hepzyme reversed these interference patterns without affecting drug-free or true LA-positive plasmas. Their use restores assay specificity and enables accurate LA interpretation when anticoagulant therapy cannot be safely interrupted, supporting incorporation of neutralization agents into routine LA testing algorithms.
No part of this publication may be reproduced, distributed, or transmitted in any form or by any means, including photocopying, recording, or other electronic or mechanical methods, without the prior written permission of the author.
No part of this publication may be reproduced, distributed, or transmitted in any form or by any means, including photocopying, recording, or other electronic or mechanical methods, without the prior written permission of the author.