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Heghine Khachatryan: How DOACs Can Cause False-Positive FVIII Inhibitor Results
Heghine Khachatryan/LinkedIn
Mar 7, 2026, 15:50

Heghine Khachatryan: How DOACs Can Cause False-Positive FVIII Inhibitor Results

Heghine Khachatryan, Editor-in-Chief of Hemostasis Today, Head of Hemophilia and Thrombosis Center at Yeolyan Hematology and Oncology Center, shared RPTH‘s post on LinkedIn:

“Direct oral anticoagulants (DOACs) have transformed the prevention and treatment of thrombosis.

However, their presence in plasma can significantly interfere with clot-based laboratory assays, including one of the most critical tests in hemophilia care — the Factor VIII inhibitor assay.

A recent brief report published in Research and Practice in Thrombosis and Haemostasis highlights an important diagnostic challenge:

DOACs may produce false-positive results in FVIII inhibitor testing, potentially leading to misinterpretation and inappropriate clinical decisions.

The study demonstrates that:

  • DOACs interfere with clot-based FVIII inhibitor assays
  • The degree of interference varies between agents
  • Activated charcoal–based DOAC removal can significantly restore assay reliability

For clinicians and laboratory specialists, this serves as an important reminder:

Accurate inhibitor diagnostics require awareness of anticoagulant interference and appropriate pre-analytical handling of samples.

Strengthening collaboration between clinical hematologists and coagulation laboratories remains essential for precise diagnosis and optimal patient care.”

Research and Practice in Thrombosis and Haemostasis shared a post on LinkedIn, about a recent article by Rick Timmerije et al, adding:

“Could anticoagulants be quietly distorting one of our most important hemophilia assays?

Direct oral anticoagulants (DOACs) are widely used, but they can create a hidden diagnostic trap.

A new RPTH study shows that DOACs can interfere with the factor VIII inhibitor (Nijmegen–Bethesda) assay, producing false-positive inhibitor results that could mislead clinical decisions.

Here’s the key signal:

  • All tested DOACs caused concentration-dependent false-positive FVIII inhibitor results.

Dabigatran produced the strongest interference, while apixaban showed the least effect.

Why this matters clinically

  • False inhibitor diagnosis
  • Unnecessary immunosuppression
  • Inappropriate use of bypassing agents
  • Delayed recognition of true acquired hemophilia

But there is a practical solution:

Activated charcoal–based DOAC removal restored assay accuracy, bringing inhibitor measurements back within normal assay variability.

Translation:

Sometimes the problem isn’t the patient, it’s the assay.

Big questions for clinicians and labs:

  • Should DOAC removal become routine before inhibitor testing?
  • How many ‘inhibitors’ might actually be assay interference?
  • Do other clot-based assays face similar hidden bias?”

Title: Direct oral anticoagulant interference and removal in the factor VIII inhibitor assay

Authors: Rick Timmerije, Saskia E.M. Schols, Daniëlle Meijer, Wideke Barteling, An K. Stroobants, Sanna R. Rijpma

Read Full Article on RPTH

Heghine Khachatryan, RPTH

Othe posts featuring Heghine Khachatryan on Hemostasis Today.

An K. Stroobants Daniëlle Meijer Direct Oral Anticoagulants DOACs FVIII Inhibitor Health Heghine Khachatryan Hematology Hemostasis Hemostasis News Hemostasis Today ISTH Medicine Research and Practice in Thrombosis and Haemostasis Rick Timmerije rpth Sanna R. Rijpma Saskia E. M. Schols the Factor VIII inhibitor assay Wideke Barteling
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