title: Comparative performance of three anti-factor Xa heparin assays in patients in a medical intensive care unit receiving intravenous, unfractionated heparin.
abstract: The availability of automated anti-Xa heparin assays provides the opportunity to manage patient unfractionated heparin levels directly, rather than by the activated partial thromboplastin time. Because critically ill patients can acquire an antithrombin deficiency, we compared the performance of 3 anti-Xa heparin assays, 1 with and 2 without antithrombin supplementation, by analyzing in vitro aliquots of plasma with defined antithrombin levels and specimens from intensive care patients receiving intravenous heparin therapy. Heparin concentration recovery, in vitro, was dependent on the plasma antithrombin concentration for all 3 assays. The antithrombin-supplemented assay demonstrated improved heparin recovery in direct correlation to the heparin concentration in the plasma. The greatest effect of antithrombin supplementation occurred when the antithrombin level dropped below 40%, a level present in only 5% of the patient specimens. Analysis of patient specimens demonstrated significant correlation among the 3 assays. Classification of the clinical adequacy of patient heparin levels showed agreement of 80% or more between the antithrombin-supplemented and nonsupplemented assays. The antithrombin-supplemented assay did not significantly improve clinical usefulness.
authors.affiliation: Department of Pathology, Division of Respiratory, Critical Care, and Occupational, Pulmonary Medicine, University of Utah Health Sciences Center, Salt, Lake City, UT 84132-2501, USA.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Lehman
authors.forename: Jonathan A
authors.initials: JA
authors.lastname: Rettmann
authors.forename: Lori W
authors.initials: LW
authors.lastname: Wilson
authors.forename: Boaz A
authors.initials: BA
authors.lastname: Markewitz
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000925:Anticoagulants / Q000494:pharmacology*; D000991:Antithrombins / Q000008:administration & dosage; D001780:Blood Coagulation Tests / Q000379:methods*; D065427:Factor Xa Inhibitors; D005260:Female; D006493:Heparin / Q000494:pharmacology*; D006801:Humans; D007362:Intensive Care Units; D008297:Male; D008875:Middle Aged; D010314:Partial Thromboplastin Time
chemical_list: D000925:Anticoagulants; D000991:Antithrombins; D065427:Factor Xa Inhibitors; D006493:Heparin