Asymptomatic Factor VII Padua in African Americans.

Background: Symptomatology in congenital human FVII deficiency with FVII:C (Factor VII Coagulant Activity) levels < 1% ranges from asymptomatic to severe hemorrhagic problems. Additionally, FVII:C differs markedly depending upon the source of tissue factor (TF) in the thromboplastin utilized for measuring FVII:C. FVII deficiency reported in 1978 in patients from Padua, Italy was later shown to be associated with an arginine (R) to glutamine (Q) mutation at FVII amino acid 304. A study by Triplett et al. from 1985 reported FVII deficiency in 26 patients including 16 Caucasians, 1 Hispanic and 9 blacks. Of these patients, all 9 black patients were asymptomatic whereas the other 17 patients had a clinically relevant bleeding disorder. Since that time there have been no reports describing the genetic cause of FVII deficiency in asymptomatic African American individuals.

Methods: Plasma was obtained from patient blood samples obtained in 3.2% sodium citrate. FVII:C levels were performed using one-stage clotting assays with either rabbit brain thromboplastin (Simplastin Excel, Biomerieux, Durham, NC) or lyophilized recombinant human TF (Innovin, Dade Behring, Inc., Newark, DE). Factor VII antigen levels (VII:Ag) were measured using an enzyme-linked immunoabsorbent assay (American Bioproducts Co, Parsippany, NJ). A normal pool was constructed by mixing equal volumes of plasma from greater than 20 healthy control subjects.

Conclusions: We show that FVII deficiency in three asymptomatic African American patients at our specialty laboratory was due to FVII-Padua (R304Q). An additional ten African American patients showed prolonged prothrombin times and FVII:C values consistent with the laboratory phenotype of FVII-Padua. This diagnosis prevented inappropriate blood transfusions prior to surgery in several of these patients.