John Libbey Eurotext



Factor IX assays in treated hemophilia B patients Volume 26, issue 1, Janvier-Février 2020

Christophe Nougier Pour le groupe d’études de la biologie des maladies hémorragiques du Groupe français d’études de l’hémostase et la thrombose 11
1 Service d’hématologie-hémostase, Hôpital Trousseau, CHU de Tours, EA 7501 Université François Rabelais, Tours, France
2 CHU Lille, Institut d’hématologie transfusion, Inserm U1011, Lille, France
3 Laboratoire d’hématologie générale, Hôpital Necker AP-HP, Paris, Université Paris Sud Saclay, Inserm U1176, Le Kremlin-Bicêtre, France
4 CHU de Rouen, UF Hémostase-hématologie biologique, Rouen, France
5 Service d’hématologie hémostase, CHU de Nancy, France
6 Laboratoire d’hématologie, Centre Hospitalier de Versailles, Le Chesnay, France
7 Laboratoire d’hématologie, Hôpital La Caval Blanche, CHU de Brest, France
8 Service d’hématologie hémostase, Groupe hospitalier régional de Mulhouse et Sud Alsace, France
9 Service d’hématologie-biologique, CHU Bicêtre, AP-HP, Université Paris Sud Saclay, Inserm U1176, Le Kremlin-Bicêtre, France
10 Service d’hématologie-hémostase, Hôpital Simone Veil, Eaubonne, France
11 Service d’hématologie hémostase, Hospices civils de Lyon, Bron, France
12 Service d’hématologie hémostase, Hôtel-Dieu, CHU de Nantes, France
13 Service d’hématologie biologique, Hôpital Pasteur, CHU Nice, France
14 Laboratoire d’hématologie, CHU de Toulouse, France
* Tirés à part

Replacement therapy with plasma-derived or recombinant FIX (pdFIX or rFIX) concentrates is the standard of treatment in patients with hemophilia B. The method predominantly used for measuring factor IX (FIX:C) levels is the one-stage clotting assay (OSA) but this method depends on the activated partial thromboplastin time (APTT) reagent and the coagulation analyzer used, and wide variations in the measurements of FIX recovery have been reported with some factor concentrates. The French study group on the biology of hemorrhagic diseases (a collaborative group of the GFHT and MHEMO network), presents a review of the literature and proposals for the monitoring of FIX:C levels in treated hemophilia B patients. The use of OSA calibrated with a plasma reference tested against the current FIX WHO International Standard is recommended for the monitoring of patients treated with pdFIX or rFIX. Chromogenic substrate assays (CSA) are adequate for the monitoring of patients treated with Rixubis®, but data available for Benefix® are currently too limited. For extended half-life rFIX (EHL-rFIX), large discordances in the FIX:C levels measured were evidenced, depending on the method and reagents used. Great attention is therefore required for measuring FIX:C levels by OSA in patients substituted by EHL-rFIX. Commercial kits for CSA are not equivalent, and although potentially useful, they are not validated for all EHL-rFIX. Most of recent studies reported data obtained with spiked plasmas, which deserve to be confirmed on plasma samples collected in treated patients.

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