A Practical Guide to Laboratory Haemostasis


Paediatric Reference Ranges


The coagulation system in the neonate is immature compared to the adult system (or the child at 6 months of age) but remarkably it results in few problems for the healthy term neonate. Reference ranges must be used for neonates and for the pre-term infant as many of the proteins involved in haemostasis vary with age.

For a review of this area and reference ranges - see Reference 4, 5 and 6.
Below is a summary of the proteins/Tests that are low/prolonged in the neonate

Procoagulant Proteins

Protein Comment
Factor II All the Vitamin K depending clotting factors are low at birth and reach adults values by 6 months of age [See Protein C and S below]
Factor VII
Factor IX
Factor X
Factor VIII Normal at birth
Factor XI Normal at birth
Factor XII Normal at birth
Von Willebrand Factor [VWF] Normal at birth
Factor XIII Normal at birth
Fibrinogen Levels are normal at birth but a fetal fibrinogen due to altered sialic acid content can

Natural Anticoagulants

Protein Comment
Protein C Low at birth and although in many cases it is normal by 6 months of age in some individuals it may take longer.
Heterozygous PC deficiency can be difficult to diagnose in the neonatal period due to the wide variation in levels. In contrast homozygous deficiency is readily diagnosed due to a complete absence of PC.
Protein S Total Protein S levels are low at birth. Protein S exists in the neonate primarily in the Free form due to the low C4b binding protein. Free PS levels are low at birth and reach adult values at ~4 months of age.
Antithrombin Functional antithrombin levels are low at birth and may be further reduced in the sick neonate. Levels normally reach adult values at ~3 months of age.
Factor V Leiden
Prothrombin G20201A Mutation
These mutations should be sought be DNA analysis (if this is indicated). APCr screening assays can be unreliable due to the variation in FVIII levels in the neonate.
Plasminogen Plasminogen levels are low at birth (~50% that of the adult).
α2-macroglobulin Levels are raised in children