A1 Refereed original research article in a scientific journal

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




AuthorsTanja Savukoski, Jenna Jacobino, Päivi Laitinen, Bertil Lindahl, Per Venge, Noora Ristiniemi, Saara Wittfooth, Kim Pettersson

Publication year2014

JournalClinical Chemistry and Laboratory Medicine

Journal name in sourceClinical chemistry and laboratory medicine : CCLM / FESCC

Journal acronymClin Chem Lab Med

Volume52

Issue7

First page 1041

Last page1048

Number of pages8

ISSN1434-6621

DOIhttps://doi.org/10.1515/cclm-2013-1044


Abstract

BACKGROUND\nCardiac 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.\nMETHODS\nThe 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.\nRESULTS\nThe 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



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