  Haemostasis is governed by a highly complex system of interacting proteins.
Due to the central role of thrombin, thrombin generation and specifically the
thrombin generation curve (TGC) is commonly used as an indicator of haemostatic
activity. Functional characteristics of the haemostatic system in neonates and
children are significantly different compared with adults; at the same time
plasma levels of haemostatic proteins vary considerably with age. However,
relating one to the other has been difficult, both due to significant
inter-individual differences for individuals of similar age and the complexity
of the biochemical reactions underlying haemostasis. Mathematical modelling has
been very successful at representing the biochemistry of blood clotting. In
this study we address the challenge of large inter-individual variability by
parameterising the Hockin-Mann model with data from individual patients, across
different age groups from neonates to adults. Calculating TGCs for each patient
of a specific age group provides us with insight into the variability of
haemostatic activity across that age group. From our model we observe that two
commonly used metrics for haemostatic activity are significantly lower in
neonates than in older patients. Because both metrics are strongly determined
by prothrombin and prothrombin levels are considerably lower in neonates we
conclude that decreased haemostatic activity in neonates is due to lower
prothrombin availability.
