... on the principle of sandwich immunoassay for determination of NT-proBNP in human blood specimens. One monoclonal antibody and ... one polyclonal antibody are employed to identify NT-proBNP specifically, resulting in one or two purplish red ... into the FIA8000 Quantitative Immunoassay Analyzer, the concentration of NT-proBNP is measured quantitatively and displayed on the screen. ...