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Licensed Unlicensed Requires Authentication Published by De Gruyter March 8, 2014

Novel sensitive cardiac troponin I immunoassay free from troponin I-specific autoantibody interference

  • Tanja Savukoski EMAIL logo , Jenna Jacobino , Päivi Laitinen , Bertil Lindahl , Per Venge , Noora Ristiniemi , Saara Wittfooth and Kim Pettersson

Abstract

Background: Cardiac troponins (cTnI and cTnT) are the recommended biomarkers of myocardial infarction. As cTn-specific autoantibodies (cTnAAb) can interfere with the cTn detection by state-of-the-art cTnI assays, our objective was to develop a sensitive cTnI immunoassay free from this analytical interference.

Methods: The assay used antibody-coated spots containing three capture Mabs/Fabs directed against the N-terminus, midfragment and C-terminus of cTnI and a europium chelate-labeled tracer Mab against the C-terminus. Following a 3-h sample incubation and washing, cTnI was quantified by time-resolved fluorometry.

Results: The limit of detection (LoD) was 2.9 ng/L and the assay was linear up to 50,000 ng/L. The total precision of 10% CV was not reached, but 20% CV was reached at 10 ng/L. Mean cTnI (10–50,000 ng/L) recoveries were 100% and 119% in three cTnAAb-positive and two cTnAAb-negative individuals, respectively, verifying the interference resistance of the antibody design used. On average, Architect hs-cTnI assay gave seven-fold higher cTnI concentrations than the new assay but the correlation between the assays was good (r=0.958). Of apparently healthy individuals (n=159), 18% had measurable cTnI values (>LoD) and 10% were cTnAAb-positive. The proportion of measurable cTnI values, however, was significantly higher in cTnAAb-positive individuals (13/16, median cTnI 8.5 ng/L) than in cTnAAb-negative individuals (15/143, median cTnI <LoD) (p<0.001).

Conclusions: Although the developed sensitive cTnI assay without cTnAAb interference takes too long for diagnostic purposes, it could serve as an important analytical tool for exploring the impact of cTnAAbs for cTn testing and for unraveling the etiology behind cTn-related autoimmune responses.


Corresponding author: Tanja Savukoski, Department of Biotechnology, University of Turku, Tykistökatu 6A 6th floor 20520 Turku, Finland, Phone: +358 2 3338091, Fax: +358 2 3338050, E-mail:

Acknowledgments

We gratefully acknowledge technical support from Liisa Hattara and Petri Saviranta (VTT Technical Research Centre of Finland) and statistical support from Tuukka Pölönen and Tero Vahlberg (University of Turku).

Conflict of interest statement

Authors’ conflict of interest disclosure: The authors stated that there are no conflicts of interest regarding the publication of this article. Research funding played no role in thestudy design; in the collection, analysis, and interpretationof data; in the writing of the report; or in the decision tosubmit the report for publication.

Research funding: T. Savukoski, DIA-NET, the Graduate School of Advanced Diagnostic Technologies and Applications.

Employment or leadership: None declared.

Honorarium: None declared.

Patent: K. Pettersson, coinventor on patent for troponin I determinations (US2008153109/EP1473567).

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Article note: Part of the results has been presented as a poster at the 20th IFCC-EFLM European Congress of Clinical Chemistry and Laboratory Medicine in Milan, 2013.


Received: 2013-12-4
Accepted: 2014-2-17
Published Online: 2014-3-8
Published in Print: 2014-7-1

©2014 by Walter de Gruyter Berlin/Boston

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