ABSTRACT
We describe a fully automated assay for determining effective heparin activity in plasma, based on heparin-catalyzed inhibition of Factor Xa (EC 3.4.21.6) by antithrombin III (AT III). Residual Factor Xa is determined kinetically by the Du Pont aca discrete clinical analyzer with a chromogenic substrate and is inversely related to heparin activity. Because the test plasma is the sole source of AT III, the assay result is dependent on AT III activity and reflects effective rather than total heparin activity. The assay range is 20-1200 USP units/L, and the assay shows equivalent sensitivity to standard and low-molecular-mass heparins. Within-run reproducibility (CV) is 1.6% at 390 units/L. There was no interference from common blood components or drugs. Results agreed well with those by the Coatest heparin kit (Kabi) adapted to the Cobas-Bio analyzer (r = 0.85, n = 122).
Subject(s)
Heparin/blood , Aniline Compounds/analysis , Antithrombin III/pharmacology , Autoanalysis/methods , Buffers , Chromogenic Compounds , Factor X/antagonists & inhibitors , Factor Xa , Humans , Hydrogen-Ion Concentration , Quality Control , Reagent Kits, Diagnostic , Reference ValuesABSTRACT
Methods for the measurement of the functional concentration of AT III, PLG, and FBG have been developed for the Du Pont aca discrete clinical analyzer. These methods are fully automated, provide excellent reproducibility, and compare favorably with existing methodologies. The availability of these and future coagulation assays on this automated analyzer will provide the hospital laboratory with a reliable means for evaluating hemostatic function. In addition, excellent method reproducibility and use of defined reference standards should significantly contribute to the standardization of coagulation methods.
