Heparin cofactor II in adults and infants with thrombosis and DIC

Heparin cofactor II (HC II) was measured by a chromogenic activity assay in normal preterm infants (gestational age, 28–36 weeks; n = 17; 29% ± 11.5 [mean ± 1 SD], range 11–51), normal full‐term infants (n = 18; 49% ± 6.6 [mean ± 1 SD], range 36–58), and normal adults (n = 38; 101% ± 14 [mean ± 1 SD], range 73–130). Normal children attained adult levels at approximately 5 to 7 months of age. The lower values in preterm and term infants most likely reflect immature liver function. Neither adults and children with a history of thrombosis with prior negative evaluation (n = 74), patients with documented protein C and protein S deficiency (n = 4), nor sick infants without evidence of consumptive coagulopathy (n = 15) had significantly lower levels of HC II activity. Infants with disseminated intravascular coagulation (n = 2) had strikingly lower levels of HC II activity.