The combined performance of the following two assays is usually assessed to identify F5F8D:
FVF8D is characterized by the prolongation of both first screening coagulation tests, with the APTT being disproportionately affected.
Specific assays of FV and FVIII coagulant activity are then necessary to evaluate the residual FV and FVIII coagulant activity. The tests depend upon the ability of a sample containing the factor under investigation to correct or shorten the delayed clotting of plasma that is completely deficient in that factor. Normal ranges can vary from laboratory to laboratory; however, the combined deficiency can be diagnosed when the coagulant factors activity levels are less than 45-50% for both FV and FVIII.
Factor antigen assays are not strictly necessary for diagnosis and treatment.
If continuous bleeding is observed after replacement therapy, the presence of an inhibitor should be investigated. The inhibitor is measured through the Bethesda assay, based on the neutralization of an external source of FV or FVIII.
Imaging techniques are not needed for minor bleeding. For major bleeding, which is extremely rare in F5F8D, the following procedures are necessary (as in all other rare coagulation disorders):
CT, computed tomography; MRI, magnetic resonance imaging.
Rare Coagulation Disorders Resource Room, an extension of the RBDD Registry (eu.rbdd.org), was developed in collaboration with the Indiana Hemophilia & Thrombosis Center (www.innovativehematology.org).
The Resource Room serves as a platform to promote international collaboration to increase knowledge of these very rare disorders and to improve the care of affected individuals. The international RBDD mission, under the leadership of Dr. Peyvandi, will continue to be expanded over time.
The Resource Room thanks all contributing authors of the website articles that have made this valuable information available to the global community of both individuals affected with rare coagulation disorders and their healthcare providers.
