Analytical and Clinical Performance of the Immulite Cardiac Troponin I Assay

Abstract

Cardiac troponin I (cTnI) is now regarded as one of the most specific markers for cardiac injury, and an increasing number of commercial methods are available. We report here a study of the Immulite cTnI assay manufactured by DPC. The Immulite cTnI assay is a sandwich immunoassay that uses a monoclonal antibody immobilized on beads and a goat polyclonal antibody labeled with alkaline phosphatase as a tracer (1); both antibodies recognize epitopes localized in the N-terminal part (residues 33–110) of the protein. The chemiluminescent substrate used for the enzymatic reaction is an ester of adamantyl dioxetane phosphate. We used as calibrators purified human cTnI in horse serum. The within- and between-run imprecisions (CV) were <3.9% and 3.6%, respectively, at a mean cTnI of 1.5 μg/L (n = 20). The minimal cTnI value quantified was 0.2 μg/L, and no detectable cTnI was observed in 20 runs of assay diluent. The lowest cTnI concentration …