Background: The diagnostic approach to haemostatic defects in the newborn is challenging and requires appropriate interpretation of coagulation tests according to reference values dependent on the postnatal age.
Methods: This investigation was designed to study the postnatal development of the human coagulation system in newborn infants and to develop appropriate reference ranges for prothrombin time (PT), activated partial thromboplastin time (APTT) and fibrinogen (FBG) according at the day of birth and for the following postnatal period (days 1, 2, 3, 4, 5, 6, from 7 to 10 and from 11 to 44).
Results: The mean FBG value was already within the adult reference range in newborns at birth, the mean PT value fell within the adult reference range in infants aged 4 days or more, whereas the mean APTT value was still higher than the upper limit of the adult reference range in infants aged between 11 and 20 days. The prevalence of infants with pathological values according to the actual adult reference ranges was limited for FBG (from 24 to 7%), decreased from 92 to 8% in infants aged 0 and 11-20 days for PT, but remained elevated throughout the observational period for APTT (from 94 to 71%).
Conclusions: The results of the present investigation demonstrate that the actual adult reference ranges for coagulation screening tests, especially PT and APTT, cannot be applied to newborns and young infants.