Pediatric reference values for molecular markers in hemostasis

Background: The hemostatic system is a developing and changing process relative to age. Objectives: To distinguish the differences in hemostatic parameters between children and adults, and to establish the normal range of these parameters in children of different age groups. Design/Methods: Blood was obtained from healthy children aged 1 to 18 years (n = 70) and adults (n = 26). Children were categorized into 3 age groups: 1 to 5 years, 6 to 10 years, and 11 to 18 years. Several coagulation and fibrinolysis parameters were determined. Results: Children in all age groups showed no significant difference in mean levels of von Willebrand factor antigen and activity, activated partial thromboplastin time, fibrinogen, activated factor VII, tissue plasminogen activator, plasminogen activator inhibitor-1, and thrombin activatable fibrinolysis inhibitor compared with adults. However, children aged I to 5 years had significantly higher mean values of soluble thrombomodulin (P = 0.001), prothrombin time (P = 0.03), tissue factor (P < 0.001), thrombin-antithrombin complex (P < 0.001), and D-dimer (P = 0.009) whereas they had significantly lower mean levels of protein C activity (P = 0.02) than did adults. Conclusions: These data indicate physiologic differences in the hemostatic system between children and adults and should serve as a useful reference guide in interpreting test results for children with suspected bleeding disorders.