ABSTRACT
We describe a prototype quantitative automated assay for fibrin and fibrinogen degradation products, a particle-enhanced turbidimetric inhibition immunoassay (PETINIA) in the Du Pont aca discrete clinical analyzer. This assay involves a latex particle reagent with covalently bound fibrinogen and a polyclonal antiserum raised in rabbits against human fibrinogen. A special secondary sample-collection tube quantitatively removes fibrinogen from citrated plasma and inhibits further fibrinolysis, independent of heparin concentration. The assay range is 0-100 mg/L, in fibrinogen equivalents. The CV for the assay is less than 10% when performed with the aca. Nonclottable fibrin and fibrinogen fragments are measured by the assay, the greatest sensitivity being directed at the E domain of the fibrinogen molecule. We illustrate with case studies the potential of this assay for providing clinical information not obtainable with currently available qualitative and semi-quantitative assays.
Subject(s)
Fibrin Fibrinogen Degradation Products/analysis , Adult , Autoanalysis , Female , Humans , Immunoassay/methods , Indicators and Reagents , Male , Middle Aged , Nephelometry and Turbidimetry , Pregnancy , Reference ValuesABSTRACT
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-microL sample volumes. In the AT III assay the sample is incubated with excess thrombin and heparin to form the functionally inactive AT III-thrombin complex. Residual thrombin is measured through its rate of hydrolysis of a lysine thioester and is inversely related to analyte concentration. In the plasminogen assay excess streptokinase is reacted with the sample to form an enzymatically active complex. The substrate hydrolysis 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 III has a range of 0 to 150% of the value for normal human plasma (% NHP) with a CV of 3% at 80% NHP. The plasminogen assay is linear from 25 to 200% NHP with a CV of less than 2% at 80% NHP. No significant interferences with either method by common blood components or drugs were found.