Childhood Coagulation Marker Levels Distinct From Adulthood

Levels of key coagulation markers significantly vary with age in children, research reveals, potentially affecting the diagnosis and treatment of pediatric thrombotic and hemorrhagic disease.

Young children have significantly lower levels of fibrinogen and factor (F)II, IX, XI, and XII than older children, the researchers report in the Journal of Thrombosis and Haemostasis.

Younger age was also associated with significantly lower levels of Protein C and Protein S, but higher concentrations of D-dimer.

Von Willebrand factor (vWF) levels were also elevated in the first year of life, but there was no associated increase in FVIII levels, expected due to the known impact of vWF on FVIII half life.

vWF levels fell to a nadir at 1 year and then gradually increased to adult levels, but this trend was dependent on blood group type. Blood group O carriers showed only a slight increase from a median of 66% to 88% of adult levels, versus a median 106% in non-O blood group carriers.

The researchers believe this may be due to the increased susceptibility of vWF of blood group O to the proteolytic activity ofADAMTS13 compared with non-O blood groups. In the first months of childhood, when A, B, and H antigens of vWF are low, there may be less pronounced blood group differences in vWF levels.

"Our results underline the need for age-specific reference ranges," write Inge Appel and co-workers, from Erasmus Medical Centre - Sophia Children's Hospital in Rotterdam, the Netherlands.

The greatest variation was between infants in the first year of life versus adults, but inter-individual variability in coagulation factors was highest in the youngest children. The researchers therefore recommend: "In neonates and infants multiple reference samples are required to define the normal range in coagulation proteins for age more precisely."

The team examined blood samples from 218 healthy children aged 1-6 months (n=29), 7-12 months (n=25), 1-5 years (n=57), 6-10 years (n=57), 11-18 years (n=50), and over 19 years (n=52) using two different analyzers; the Behring Coagulation System (Siemens Healthcare Diagnostics Products GmbH, Marburg, Germany) and the CA-1500 system (Sysmex, Kobe, Japan).

There was good correlation between the two systems for all coagulation markers, except prothrombin and activated partial thromboplastin time.