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The Fiix-PT Assay; Improves on PT-INR?

I [Geo] received a communication from Dr. Pall Onundarson, Hematology Laboratory and Thrombosis and Hemostasis Service, Faculty of Medicine, University of Iceland, Reykjavik, Iceland, about the Fiix-PT assay designed to monitor vitamin K antagonist [warfarin, Coumadin] therapy unaffected by reductions in FVII and FIX which the authors claim to play little role in clinical anticoagulation. I’ve attached two articles that describe the assay in detail. Dr. Onundarson speculates the assay could also be adapted to anti-Xa DOAC measurement.

Onundarson PT, Palsson R, Witt DM, Gudmundsdottir BR. Replacement of traditional prothrombin time monitoring with the new Fiix prothrombin time increases the efficacy of warfarin without increasing bleeding. A review article. Thrombosis Journal 2021:

Oskarsdottir AR, Gudmundsdottir BR, Jensdottir HM, et al. Ignoring instead of chasing after coagulation factor VII during warfarin management: an interrupted time-series study. Blood. 2021; 137: 2745–55. doi: 10.1182/blood.2020008698: 10.1182/blood.2020008698.

Today, 2-2-22, I [Geo] received a relevant communication from researcher David McGlasson who published the attached 2000 study, McGlasson DL, Beard BM. Unexpected levels of FVII when monitoring coumadin patients with unstable INR’s  Clin Hemost Rev. October 2000.8–9. This study surprisingly documented near-normal factor VII levels in anticoagulated patients.

Comments (1)
Anticoagulant Therapy
Pall T. Onundarson
Feb 1, 2022 2:17am

Thank you, George, for
Thank you, George, for posting this. The FiixNR is a CE marked product available from in Europe. In our two clinical studies monitoring warfarin with Fiix normalized ratio (FiixNR) instead of PTINR, TE was reduced about 50% during long-term management. This appears to be due to stabilization of the anticoagulant effect by ignoring FVII. There was no increase in bleeding. There is no question that unmonitored DOAC treatment is more convenient than warfarin and clinical studies suggest that DOACs are similarly effective but safer. However, now the question remains to be answered how FiixNR monitored warfarin compares to the DOACs. We hope to have such results later in year 2022. For patients remaining on warfarin for various reasons we think a more stable effect will be welcomed.

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