Chimeric recombinant antibody fragments in cardiac troponin I immunoassay

Objectives: To introduce a novel nanoparticle-based immunoassay for cardiac troponin I (cTnl) utilizing chimeric antibody fragments and to demonstrate that removal of antibody Pc part and antibody chimerization decrease matrix related interferences. Design and methods: A sandwich-type immunoassay for cTnI based on recombinant chimeric (mouse variable/human constant) antigen binding (drab) antibodies and intrinsically fluorescent nanoparticles was developed. To Lest whether using chimeric antibody fragments helps to avoid matrix related interferences, samples (n 39) with known amounts of triglycerides, bilirubin, rheumatoid factor (RF) or human anti-mouse antibodies (HAMAs) were measured with the novel assay, along with a previously published nanoparticle-based research assay with the same antibody epitopes. Results: The limit of detection (LoD) was 3.30 ng/L. Within-laboratory precision for 29 ng/L and 2819 ng/LcTnI were 137% and 15.9%, respectively. Regression analysis with Siemens ADVIA Centaur (R) yielded a slope (95% confidence intervals) 01 0.18 (0.17-1.19) and a y-intercept of -1.94 (-128-3.91) ng/L. When compared to a previously published nanoparticle-based assay, the novel assay showed substantially reduced interference in the tested interference prone samples, 15.4 vs. 51.3%. A rheumatoid factor containing sample was decreased from 241 ng/L to <LoD. Conclusions: Utilization of cFab-fragments enabled the development of a sensitive (LoD = 3.3 ng/L) immunoassay for the detection of cTnl and decreased matrix related interferences, thus resulting in a lower number of falsely elevated cTnI-values. (C) 2014 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.