Newborn factor VIII complex: elevated activities in term infants and alterations in electrophoretic mobility related...

The factor VIII coagulant activity (FVIII:C), factor VIII related antigen (FVIII:RAG), and factor VIII ristocetin cofactor activity (FVIII:RCF) was determined in the cord blood samples of 30 healthy term newborns. Sodium citrate anticoagulant, cold, and a proteolytic inhibitor were used in sample processing. All three factor VIII activities were elevated in infants compared to adults; additionally, FVIII:RAG was significantly higher in vaginally compared with caesarean section delivered infants. Crossed immunoelectrophoresis of the term infant plasma showed a consistently normal factor VIII mobility. An additional group of 22 sick premature and term infants had determinations of factor VIII antigen and crossed immunoelectrophoresis. The FVIII:RAG of sick infants was approximately twice that of the well term infants. Infants with severe lung disease, asphyxia, thrombosis and sepsis had normal electrophoretic mobility despite marked elevations in FVIII:RAG. Abnormal, symmetrical, more anodal migrations were seen only in a group of severely ill newborns with dissiminated intravascular coagulation (DIC) or signs of activated fibrinolysis. These results suggest that the elevated FVIII activities seen in well infants and most sick newborns are the result of increased release of a normal form of the FVIII molecule. Those elevations seen in sick newborns with DIC result from increased release and the production of an altered, faster moving FVIII molecule.