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In Vitro DOAC Removal Agents

Wenxiong He [“Wen”], Toronto, Canada, is a participant in the Rutgers University graduate course CLSC 5124, Advanced Hemostasis. Wen is in the hematology lab at St. Michael’s Hospital in Toronto which includes the special coagulation lab. Wen offered this information about the use of a DOAC removal agent:

“Our lab uses a DOAC removal product from 5-Diagnostics called ‘DOAC-Remove.’ We don’t use it on every patient prior to our thrombophilia profile assay (APCR, protein C, protein S, AT, LAC panel). We only use it when the physician indicates that the patient is on DOACs and the PT/INR from the patient is prolonged/elevated. Our IL HemosIL protein S assay is a PT-based assay and may be affected.

Based on my observation, when the patient is on DOAC, especially apixaban, and the IL DRVVT LAC screen and confirmation are done, the result will be falsely decreased. For normal donors, the DRVVT screen and confirm results are similar, thus giving us a ratio of close to 1. DOAC patients may push this number to around 0.7.

This can be an issue when we are dealing with DOAC patients who have close to cutoff DRVVT results (in our hospital, it’s 1.17). Our medical director gives us room for independent judgment. When we see a patient indicated on DOAC, with a slightly prolonged/elevated PT/INR, and the DRVVT result is close to 1.17. We will definitely do a DOAC remove and repeat the whole thing.”

Course director Elaine Keohane, PhD asked: A question came up about using products to absorb out DOACs from patient plasma before doing a thrombophilia profile to avoid interference from direct thrombin inhibitors and direct FXa inhibitors. There are at least 3 products available: DOAC-Stop, DOAC-Remove and DOAC Filter. So I asked Prof Fritsma, are labs using DOAC removal agents before testing? Are they RUO in the US?

I [Geo] answered yes to both. Though most are approved in Europe, none has been approved by the US FDA although many facilities use them as RUO tools. There are several pubs showing no interference with clot-based assays. Below I’ve linked a 2023 review of three in vitro DOAC removal devices. DOAC-Stop was the first, developed by Dr. Thomas Exner in Sydney. I’ve also attached a link to a 2020 Annals of Blood article by Dave McGlasson and me. Because DOAC therapy is not indicated in chronic APS, it may be that except for initial diagnosis, there may be little need to employ DOAC removal agents for chronic APS patients.

Here is an 11-8-23 comment from Jennifer J. Kiblinger, Scientific Director, DiaPharma Group, Inc. DOAC-Stop™ is the original DOAC neutralizer, readily available in North America through DiaPharma and labeled for Research Use Only, not for use in diagnostic procedures, as you mention. We also have Inhibitor Tubes containing DOAC samples to spike plasmas for in-house evaluations of DOAC-Stop™.

Here is an 11-11-23 follow-up comment from Ali Sadeghi-Khomami, Ph.D., research director at Precision BioLogic Inc.: George, you are correct. DOAC-STOP (Haematex) and DOAC-Remove (5-Diagnostics) are not FDA-cleared products yet. DOAC-Filter (Stago) is discontinued from the European market.

DOAC interferences vary among commercial DRVVT reagents and various analyzers. This is one of the reasons that in general, LA testing in the presence of DOACs is not recommended. Characterization of each assay system is advised. We have reported the effect of DOACs on frequently used commercial DRVVTs and multiple coagulometers in ISTH-2020 (Poster# PB0669, attached). Although we did not investigate the lot-to-lot variation of DRVVT-DOACs interferences in our study, our results support Wen’s observation about apixaban interference with IL’s DRVVT reagent. Apixaban reduces IL’s DRVVT ratio in both normal and LA-positive plasma samples (potential false negative) using IL’s TOP analyzer in an in vitro controlled experiment.

And here is a subsequent follow-up also on 11-11-23 from Emmanuel J. Favaloro, Ph. D., Department of Haematology, Institute of Clinical Pathology and Medical Research (ICPMR), NSW Health Pathology, Westmead Hospital, Westmead, New South Wales, Australia:

Hi all, I only have personal experience with DOAC-Stop, but I wrote an open access review, Favaloro EJ, Pasalic L. Lupus anticoagulant testing during anticoagulation, including direct oral anticoagulants. Res Pract Thromb Haemost. 2022;6:e12676. doi: 10.1002/rth2.12676.

All the DOACs affect LA testing, with dabigatran and rivaroxaban potentially yielding false positives–something we also highlighted from EQA data in the late 2010s. Apixaban behaves differently and can lead to false negatives. I’ve been told that apixaban can also lead to false positives, but haven’t seen this data–might be LA reagent-dependent. These patterns emerge since the DOACs affect screen and confirm assays differently, so that dabigatran and rivaroxaban can lead to false high LA screen/confirm ratios and apixaban to false low screen/confirm ratios. DOAC-Stop, and the other DOAC neutralizers according to the literature, can neutralise the DOAC activity. For rivaroxaban, we even showed that neutralisation by DOAC Stop for LA testing was better than by andexanet alfa. We also showed this pattern in an audit of LA requests from our lab, and contrary to popular belief, many of these patients are on DOACs!

Dr. Favaloro provided additional references available from their publishers:

  • Exner T, Rigano J, Favaloro EJ. The effect of DOACs on laboratory tests and their removal by activated carbon to limit interference in functional assays. Int J Lab Hematol. 2020;42 Suppl 1:41-48. doi: 10.1111/ijlh.13196.
  • Bonar R, Favaloro EJ, Mohammed S, et al. The effect of dabigatran on haemostasis tests: a comprehensive assessment using in vitro and ex vivo samples. Pathology. 2015;47:355–64. doi: 10.1097/PAT.0000000000000252.
  • Bonar R, Favaloro EJ, Mohammed S, Ahuja M, et al. The effect of the direct factor Xa inhibitors apixaban and rivaroxaban on haemostasis tests: a comprehensive assessment using in vitro and ex vivo samples. Pathology. 2016;48:60–71. doi: 10.1016/j.pathol.2015.11.025.
  • Favaloro EJ, Mohammed S, Curnow J, Pasalic L. Laboratory testing for lupus anticoagulant (LA) in patients taking direct oral anticoagulants (DOACs): potential for false positives and false negatives. Pathology. 2019;51:292–300. doi: 10.1016/j.pathol.2018.11.008.
  • Favaloro EJ, Gilmore G, Arunachalam S, et al. Neutralising rivaroxaban induced interference in laboratory testing for lupus anticoagulant (LA): A comparative study using DOAC Stop and andexanet alfa. Thromb Res. 2019;180:10–19. doi: 10.1016/j.thromres.2019.05.013.
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