The (Fab)ulous Destiny of Idarucizumab: Highlighting Its Interference with Urine Protein Immunofixation

• Main Authors: Nicolas Gendron, Héloïse Flament, Elena Litvinova, Sofia Ortuno, Nadine Ajzenberg, Dorothée Faille
• Format: Article
• Language: English
• Published: Georg Thieme Verlag KG 2019-07-01
• Series: TH Open
• Subjects: idarucizumab; dabigatran; reversal; immunofixation; paraprotein
• Online Access: http://www.thieme-connect.de/DOI/DOI?10.1055/s-0039-1697642

Idarucizumab is a humanized antigen binding fragment (Fab) of a recombinant anti-dabigatran monoclonal antibody (IgG1-kappa) that allows rapid and sustained reversal of dabigatran-induced anticoagulation in case of bleeding or urgent surgery. Herein, we report a very unusual case of dabigatran reversal by idarucizumab in a 79-year-old woman with acute kidney failure admitted to a hospital in a context of hemoptysis. Three repeated injections were necessary because of massive dabigatran overdose and high rebounds of dabigatran plasma concentration. Idarucizumab was found on urine immunofixation up to 6 days after the last injection where it reacted with anti-kappa light chain antibody, but not with anti-gamma heavy chain antibody. Physicians should be aware of the increased half-life of idarucizumab in this context of acute kidney impairment and of its interference with urine immunofixation because it could lead to false-positive results and misdiagnosis of a paraprotein.