Chromogenic factor VIII activity assay.

Factor VIII (FVIII) may be measured by three different methodologies in the clinical laboratory: one-stage clotting assay, two-stage clotting assay, and chromogenic assay. These assays differ in ease of use, variety of reagents available, sensitivity to mild hemophilia A, and interference from lupus anticoagulants. This review will outline the methodology for each of the FVIII activity assays, with a discussion of assay interferences and variability. In some cases, chromogenic FVIII activity assays may be preferable to clot-based assays, and these clinical situations will be reviewed as well.