CC BY-NC-ND 4.0 · Semin Thromb Hemost 2023; 49(06): 609-620
DOI: 10.1055/s-0042-1758870
Review Article

Factor VIII and Factor IX Activity Measurements for Hemophilia Diagnosis and Related Treatments

Annette E. Bowyer
1   Department of Coagulation, Royal Hallamshire Hospital, Sheffield, United Kingdom
Robert C. Gosselin
2   Hemostasis and Thrombosis Center, University of California, Davis Health System, Sacramento, California
› Author Affiliations


Accurate measurement of clotting factors VIII (FVIII) or IX (FIX) is vital for comprehensive diagnosis and management of patients with hemophilia A or B. The one-stage activated partial thromboplastin time (aPTT)-based clotting assay is the most commonly used method worldwide for testing FVIII or FIX activities. Alternatively, FVIII and FIX chromogenic substrate assays, which assess the activation of factor X, are available in some specialized laboratories. The choice of reagent or methodology can strongly influence the resulting activity. Variation between one-stage FVIII or FIX activities has been reported in the measurement of some standard and extended half-life factor replacement therapies and gene therapy for hemophilia B using different aPTT reagents. Discrepancy between one-stage and chromogenic reagents has been demonstrated in some patients with mild hemophilia A or B, the measurement of some standard and extended half-life factor replacement therapies, and the transgene expression of hemophilia A and B patients who have received gene therapy. Finally, the measurement of bispecific antibody therapy in patients with hemophilia A has highlighted differences between chromogenic assays. It is imperative that hemostasis laboratories evaluate how suitable their routine assays are for the accurate measurement of the various hemophilia treatment therapies.

Publication History

Article published online:
06 December 2022

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  • 133 EMA. Accessed August 23, 2022 at:
  • 134 EMA. Accessed August 23, 2022 at:
  • 135 EMA. Accessed August 23, 2022 at:
  • 136 EMA. Accessed August 23, 2022 at:
  • 137 EMA. Accessed August 23, 2022 at:
  • 138 EMA. Accessed August 23, 2022 at: