In neonates, despite poor platelet function in various in vitro tests, closure times (CTs) in PFA-100 measurements are shorter than in adults. Neonates have a higher polymeric von Willebrand factor (vWF). They also have a higher haematocrit and higher white blood cell count than adults. which may interfere with the evaluation of platelet and vWF function by means of the PFA-100 in neonates. To assess the role of different blood constituents on neonatal CTs, red blood cell, platelet and white blood cell counts in cord blood were modified. These modifications did not provide any evidence that the difference in number between adult and neonatal blood cells was responsible for shorter neonatal CTs. In further experiments, platelets and/or vWF were inhibited by means of abciximab and anti-vWF antibody, and mixing experiments with neonatal platelet-rich and platelet-poor plasma were performed. The results showed that short cord blood PFA-100 CTs were caused by a constituent of neonatal platelet-poor plasma, probably the neonatal high multimeric vWF.
Conclusion: This study demonstrates that CTs in neonates are dependent on the same components, platelets and vWF, as in adults, making it likely that the PFA-100 can be used in neonates in the same way as in adults to investigate platelet and vWF function.