Factor VIII activity and antigen in sick newborns with pathological proteolysis in blood.

Factor VIII clotting activity (VII:C) and factor VIII related antigen (VIII:R:AG) were determined in 12 sick newborn infants with pathological proteolysis in their circulation. A marked discrepancy was noted between VIII:R:AG and VIII:C, the ratio in sick infants being, on average, 2:1, while no discrepancy was seen in healthy newborns. The finding in the sick infants resembled a low grade plasminogen activation, which was studied experimentally. It is concluded that demonstration of a marked discrepancy between VIII:R:AG and VIII:C is a useful indication of pathologic proteolysis in sick newborns.