NORMAL LEVELS OF THE NATURAL ANTICOAGULANTS (PROTEINS C-AND-S AND ANTITHROMBIN-III) AND THE FIBRINOLYTIC FACTORS (TPA AND PAI) IN ARAB CHILDREN

The diagnosis of many hemostatic defects in infancy and childhood depe nds on the establishment of normal levels of various hemostatic factor s. In this study, measurements of the natural anticoagulants (proteins C, S, and antithrombin III), as well as the fibrinolytic factors (tPA and PAI) were undertaken in healthy neonates (cord blood, n = 56), as well as in healthy children, up to 12 years of age (n = 103). The res ults were compared to normal adult values obtained from blood donors ( n = 49). Neonatal values were found to be 50% of those obtained in adu lts and their mean concentrations were as follows: ATIII antigen = 48. 4%, ATIII activity = 61.6%: protein C antigen = 47.7%, protein C activ ity = 57.2%, total protein S = 41.8% and tPA = 1.9 ng/mL. PAI level (2 5.7 ng/mL) was similar to adult values. In the first three years of li fe, almost all the hemostatic factors, other than PAI, gained adult le vels. The diminished concentrations of the natural anticoagulants, in addition to the hypofibrinolysis in neonates, shifts the hemostatic ba lance towards fibrin formation and safeguards effective hemostasis. Th e values obtained in this study may serve as local reference values.