title: Beta (β)-antithrombin activity in children and adults: implications for heparin therapy in infants and children.
abstract: BACKGROUND
  Antithrombin, a hemostatic protein and naturally occurring anticoagulant, is a major thrombin inhibitor. The capacity of antithrombin to inhibit thrombin is known to increase a 1000-fold whilst in the presence of unfractionated heparin. β-antithrombin is an isoform of antithrombin with a high affinity for unfractionated heparin. This study aimed to determine the differences in the anticoagulant activity of the β-antithrombin isoform in children compared with adults.
  
  
  METHODS
  Plasma samples were obtained from 105 healthy individuals from the following age groups: neonates (day 1 and day 3), 28 days to 1 year, 1-5 years, 6-10 years, 11-16 years and adults. The method utilized to measure the activity of β-antithrombin in plasma is a modified version of the total antithrombin assay routinely used in diagnostic laboratories. The modified version of this assay allows for the specific quantification of the β-antithrombin glycoform anticoagulant activity alone, as the β-antithrombin molecule is activated under a high salt concentration, which in turn does not allow activation of other antithrombin isoforms.
  
  
  CONCLUSIONS
  This study demonstrated that there are no age-specific differences in the activity of β-antithrombin. However, considering that the total AT activity is significantly reduced in neonates, our results suggest that in this population β-antithrombin activity is a major contributor to the overall activity of AT.
authors.affiliation: Murdoch Childrens Research Institute, Royal Children's Hospital, Parkville, Vic., Australia.
authors.forename: V
authors.initials: V
authors.lastname: Karlaftis
authors.forename: G
authors.initials: G
authors.lastname: Sritharan
authors.forename: C
authors.initials: C
authors.lastname: Attard
authors.forename: J
authors.initials: J
authors.lastname: Corral
authors.forename: P
authors.initials: P
authors.lastname: Monagle
authors.forename: V
authors.initials: V
authors.lastname: Ignjatovic
mesh_terms: D000293:Adolescent; D000328:Adult; D000925:Anticoagulants / Q000627:therapeutic use; D000991:Antithrombins / Q000737:chemistry*; D001780:Blood Coagulation Tests; D002648:Child; D002675:Child, Preschool; D006493:Heparin / Q000627:therapeutic use*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D010372:Pediatrics; D010949:Plasma / Q000737:chemistry*; D020033:Protein Isoforms / Q000737:chemistry; D013917:Thrombin / Q000737:chemistry
chemical_list: D000925:Anticoagulants; D000991:Antithrombins; D020033:Protein Isoforms; D006493:Heparin; D013917:Thrombin
keywords: anticoagulants; antithrombin III; blood coagulation factors; heparin; pediatrics