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Reducing the effect of DOAC interference in laboratory testing for factor VIII and factor IX: A comparative study using DOAC Stop and andexanet alfa to neutralize rivaroxaban effects

Favaloro, E.J., Gilmore, G., Bonar, R., Dean, E., Arunachalam, S., Mohammed, S. and Baker, R. (2020) Reducing the effect of DOAC interference in laboratory testing for factor VIII and factor IX: A comparative study using DOAC Stop and andexanet alfa to neutralize rivaroxaban effects. Haemophilia . Early View.

Link to Published Version: https://doi.org/10.1111/hae.13930
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Abstract

Introduction
Investigation of factors (F) VIII and IX is common, with testing important for diagnosis or exclusion of haemophilia A or B, associated acquired conditions and factor inhibitors. Rivaroxaban, a common direct anti‐Xa agent, causes significant interference in clotting assays, including substantial false reduction of factor levels.

Aim
To assess whether rivaroxaban‐induced interference of FVIII and FIX testing could be neutralized.

Materials and methods
An international, cross‐laboratory exercise for FVIII (n = 84) and FIX (n = 74), using four samples: (A) pool of normal plasma; (B) pool spiked with rivaroxaban (200 ng/mL); (C) rivaroxaban sample subsequently treated with ‘DOAC Stop’ and; (D) rivaroxaban sample treated with andexanet alfa (200 μg/mL). Testing performed blind to sample type.

Results
All laboratories reported normal FIX and 94% reported normal FVIII in the pool sample. Instead, 55% and 95%, respectively, reported abnormal FIX and FVIII levels for the rivaroxaban sample. DOAC Stop treatment evidenced a correction in most laboratories (100% reported normal FIX and 86% normal FVIII). Andexanet alfa provided intermediate results, with many laboratories still reporting abnormal results (59% for FVIII, 18% for FIX). We also identified reagent‐specific issues.

Conclusions
As expected, rivaroxaban caused false low values of FVIII and FIX. This might lead to increased testing to identify the cause of low factor levels and potentially lead to false identification of (mild) haemophilia A or B if unrecognized by clinicians/laboratories. DOAC Stop effectively neutralized the rivaroxaban effect, but andexanet alfa less so, with reagent‐related effects evident, and thus, false low values sometimes persisted.

Item Type: Journal Article
Murdoch Affiliation: Western Australian Centre for Thrombosis and Haemostasis (WACTH)
Publisher: Blackwell Publishing Inc.
Copyright: © 2020 John Wiley & Sons Ltd
URI: http://researchrepository.murdoch.edu.au/id/eprint/54586
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