Discrepancy between one-stage and chromogenic factor VIII activity assay results can lead to misdiagnosis of haemophilia A phenotype

SummarySeverity of bleeding phenotype in hemophilia A (HA) depends on the underlying mutation in the F8 gene and, ultimately, on the concentration and functional integrity of the factor VIII (FVIII) protein in circulating plasma. Initial diagnosis for HA and monitoring of treatment is typically performed by measuring of FVIII activity by either one-stage assay or chromogenic assay.We review evidence for why both types of assay do not give comparable results in a significant proportion of patients with non-severe haemophilia A and why the discrepancy in results between both methods segregates with distinct subcla…