title: Chimeric recombinant antibody fragments in cardiac troponin I immunoassay.
abstract: OBJECTIVE
  To introduce a novel nanoparticle-based immunoassay for cardiac troponin I (cTnI) utilizing chimeric antibody fragments and to demonstrate that removal of antibody Fc-part and antibody chimerization decrease matrix related interferences.
  
  
  METHODS
  A sandwich-type immunoassay for cTnI based on recombinant chimeric (mouse variable/human constant) antigen binding (cFab) antibodies and intrinsically fluorescent nanoparticles was developed. To test 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 3.30ng/L. Within-laboratory precision for 29ng/L and 2819ng/L cTnI were 13.7% and 15.9%, respectively. Regression analysis with Siemens ADVIA Centaur® yielded a slope (95% confidence intervals) of 0.18 (0.17-1.19) and a y-intercept of 1.94 (-1.28-3.91) 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 241ng/L to <LoD.
  
  
  CONCLUSIONS
  Utilization of cFab-fragments enabled the development of a sensitive (LoD=3.3ng/L) immunoassay for the detection of cTnI and decreased matrix related interferences, thus resulting in a lower number of falsely elevated cTnI-values.
authors.affiliation: University of Turku, Department of Biotechnology, Tykistökatu 6 A, 20520 Turku, Finland. Electronic address: heidi.hyytia@utu.fi.
authors.forename: Heidi
authors.initials: H
authors.lastname: Hyytiä
authors.affiliation: University of Turku, Department of Biotechnology, Tykistökatu 6 A, 20520 Turku, Finland.
authors.forename: Taina
authors.initials: T
authors.lastname: Heikkilä
authors.affiliation: University of Turku, Department of Biotechnology, Tykistökatu 6 A, 20520 Turku, Finland.
authors.forename: Eeva-Christine
authors.initials: EC
authors.lastname: Brockmann
authors.affiliation: University of Turku, Department of Biotechnology, Tykistökatu 6 A, 20520 Turku, Finland.
authors.forename: Henna
authors.initials: H
authors.lastname: Kekki
authors.affiliation: NordLab Oulu, Oulu University Hospital, Oulu, Finland; Department of Clinical Chemistry, University of Oulu, Oulu, Finland.
authors.forename: Pirjo
authors.initials: P
authors.lastname: Hedberg
authors.affiliation: NordLab Oulu, Oulu University Hospital, Oulu, Finland; Department of Clinical Chemistry, University of Oulu, Oulu, Finland.
authors.forename: Tarja
authors.initials: T
authors.lastname: Puolakanaho
authors.affiliation: University of Turku, Department of Biotechnology, Tykistökatu 6 A, 20520 Turku, Finland.
authors.forename: Timo
authors.initials: T
authors.lastname: Lövgren
authors.affiliation: University of Turku, Department of Biotechnology, Tykistökatu 6 A, 20520 Turku, Finland.
authors.forename: Kim
authors.initials: K
authors.lastname: Pettersson
mesh_terms: D000818:Animals; D001323:Autoantibodies / Q000276:immunology* / Q000378:metabolism; D002678:Chimera / Q000276:immunology* / Q000378:metabolism; D006801:Humans; D007118:Immunoassay / Q000379:methods; D007128:Immunoglobulin Fragments / Q000276:immunology* / Q000378:metabolism; D051379:Mice; D011485:Protein Binding / Q000502:physiology; D011994:Recombinant Proteins / Q000276:immunology* / Q000378:metabolism; D019210:Troponin I / Q000276:immunology* / Q000378:metabolism
chemical_list: D001323:Autoantibodies; D007128:Immunoglobulin Fragments; D011994:Recombinant Proteins; D019210:Troponin I
keywords: Chimeric antibody fragments; Immunoassay; Troponin I