Developmentand AnalyticalPerformanceof AutomatedTests for

We describe assays for functional antithrombin III (AT III) and plasminogen in plasma with the Du Pont aca ’ discrete clinical analyzer. Both are two-stage kinetic assays, based on synthetic substrate methodologies, and require 20-FL sample volumes. In the AT III assay the sample is incubated with excess thrombin and heparin to form the functionally inactive AT Ill-thrombin complex. Residual thrombin is mea-sured through its rate of hydrolysis of a lysine thioester and is inversely related to analyte concentration. In the plasmino-gen assay excess streptokinase is reacted with the sample to form an enzymatically active complex. The substrate hydroly-sis rate of this complex is measured, which is linearly related to the concentration of plasminogen in the sample. Reaction conditions for both assays were optimized by univariate and response surface techniques. The assay for AT Ill has