Discrepancy between the results of one-stage and chromogenic factor VIII:C assays in patients with mild/moderate hemophilia A

Diagnosis of hemophilia A is generally based on the measurement of plasma factor VIII activity (FVIII:C) using the one-stage assay (OSA) or the two-stage chromogenic substrate assay (CSA). The results of these methods show considerable discrepancy in about one-third of non-severe hemophilia A patients. The aim of this study was to assess the prevalence of FVIII:C assay discrepancy in non-severe hemophilia A patients in Iran and the relationship between the bleeding tendency with the level of FVIII:C by each method. Patients registered as mild or moderate hemophilia A in hemophilia clinic of Imam Khomeini Hospital were included. In each patient, FVIII:C level was assessed using one-stage (FVIII:C1) and chromogenic (FVIII:CR) methods. Assay discrepancy was defined as a two-fold or greater difference between the results of two assays. Bleeding tendency of the patients was recorded based on 'ISTH-BAT'. Sixty male patients were eligible for the study. The levels of FVIII:C1 was higher than FVIII:CR in 90% of patients. Assay discrepancy was seen in 41 (68%) patients. The classification of hemophilia A in 23 (38%) patients was modified by chromogenic method. No significant correlation was noted between the results of ISTH BAT with FVIII:C levels of each method. Regarding the prevalence of FVIII:C assay discrepancy in 2/3 of our non-severe hemophilia A patients, high rate of disease severity modification by chromogenic method and no significant relation between the clinical bleeding phenotype with any method, the authors highly recommend to perform both FVIII:C assays for the diagnosis and classification of non-severe hemophilia A.