VON-WILLEBRAND FACTOR-COLLAGEN BINDING-ACTIVITY IS INCREASED IN NEWBORNS AND INFANTS

von Willebrand factor (VWF) antigen (vWF:Ag) and vWF-collagen binding activity (vWF:CBA) were measured in plasma by parallel quantitative EL ISAs in normal newborns and infants (n=71). The medians for vWF:Ag (IU /ml) and vWF:CBA (U/ml), respectively, were 1.46 and 1.91 for 2-7 day- old (n=43), 1.22 and 1.40 for 2-4 week-old (n=14), 1.22 and 1.15 for 2 -6-month-old (n=14) infants and 0.98 and 1.08 (n=36) in normal adults. Elevated levels of vWF:Ag, but particularly vWF:CBA were seen for up to 4 weeks of life reaching adult levels between 2 and 6 months of lif e. The elevated levels of the vWF parameters indicate that caution sho uld be exercised when interpreting laboratory data and diagnosing von Willebrand disease in newborns and young infants and warrant the use o f age-specific reference ranges. The efficient haemostasis observed du ring early neonatal life may in part be due to the increased ability o f vWF to interact with collagen.