Both one-stage and chromogenic factor VIII assays are required for the diagnosis of mild hemophilia A.

If a diagnosis of mild hemophilia A (MHA) is missed, there can be serious consequences for a patient, particularly when surgery is required. For many years, most hemophilia centers worldwide have used one-stage activated partial thromboplastin time (APTT)-based assays for the diagnosis of hemophilia A [ [1] Over J. Methodology of the one-stage assay of factor VIII (VIII: C). Scand J Haematol Suppl. 1984; 41: 13-24 PubMed Google Scholar , [2] van Moort I. Meijer P. Priem-Visser D. van Gammeren A.J. Péquériaux N.C.V. Leebeek F.W.G. Cnossen M.H. de Maat M.P.M. Analytical variation in factor VIII one-stage and chromogenic assays: experiences from the ECAT external quality assessment programme. Haemophilia. 2019; 25: 162-169 Crossref PubMed Scopus (15) Google Scholar ]. An alternative option emerged after the group of Rosén [ [3] Rosén S. Assay of factor VIII: C with a chromogenic substrate. Scand J Haematol Suppl. 1984; 33: 139-145 Crossref Scopus (86) Google Scholar ] developed a novel and elegant approach to assay Factor VIII activity using a chromogenic assay. Color development was generated by FXa-driven cleavage of an artificial substrate in purified systems that minimized interference and eliminated many of the problems caused by the lack of specificity of APTT for FVIII activity. The uptake of chromogenic FVIII assays has progressed at different rates in different countries, but the one-stage assay remains the assay of choice in many regions [ [2] van Moort I. Meijer P. Priem-Visser D. van Gammeren A.J. Péquériaux N.C.V. Leebeek F.W.G. Cnossen M.H. de Maat M.P.M. Analytical variation in factor VIII one-stage and chromogenic assays: experiences from the ECAT external quality assessment programme. Haemophilia. 2019; 25: 162-169 Crossref PubMed Scopus (15) Google Scholar ]. Therefore, although some laboratories have the one-stage and chromogenic FVIII assays available, many laboratories only have 1 type, which is usually the one-stage assay.