Concizumab, an anti-tissue factor pathway inhibitor (TFPI) antibody for prophylaxis in haemophilia, enhances tissue factor (TF)-initiated coagulation by preventing inhibition of activated factor X (FXa), thus increasing thrombin generation.<h4>Objectives</h4>To evaluate a modified ROTEM assay for monitoring patients on concizumab prophylaxis.<h4>Methods</h4>The TF reagent (r_exTEM) was diluted 50,000-fold to make the ROTEM assay sensitive to haemophilia and to concizumab. This evidence concerns the gene F3 and hemophilia.