Method validation and clinical utility of chromogenic factor VIII assay compared to one-stage assay

The chromogenic FVIII assay is currently considered the gold standard for quantitation of factor VIII levels in both haemophilia A patients and as part of screening for thrombophilia. A method validation and evaluation of clinical utility within a routine diagnostic laboratory was undertaken by comparing the currently used one-stage assay to a commercially available chromogenic assay (Siemens, Johannesburg, South Africa). In total, 60 samples were included in this study to encompass the whole diagnostic range of the assay. Both low and high values showed very good correlation on linear regression analysis with correlation coeffients of 0.949 and 0.888 respectively. However, the lower detection limit of the Siemens Chromogenic assay was 1.5 IU/dL rendering it impossible to utilize in the setting of classifying a haemophilia A patient in terms of disease severity. Although the Siemens FVIII chromogenic assay shows excellent correlation to the currently used one-stage assay, the relatively high detection limit restrict implementation as a stand-alone assay in a routine diagnostic laboratory.