Document Detail

Comparison of cardiac troponin I immunoassays variably affected by circulating autoantibodies.
MedLine Citation:
PMID:  15718488     Owner:  NLM     Status:  MEDLINE    
BACKGROUND: We recently provided evidence that circulating autoantibodies against cardiac troponin I (cTnI) or the troponin complex cause negative interference in cTnI immunoassays. By comparing three cTnI immunoassays, we further explored the phenomenon of circulating autoantibodies and their consequences in patient samples. METHODS: We developed a cTnI immunoassay with a novel assay design using three antibodies, two of which bind epitopes outside the stable, central part of cTnI. Samples from 541 chest pain patients were measured with the new cTnI assay and with a first-generation cTnI assay (Innotrac Aio cTnI) using a conventional midfragment assay design. Using another sample cohort, we also compared the new assay with a second-generation cTnI assay (Access AccuTnI). RESULTS: The analytical detection limit of the new cTnI assay was 0.012 microg/L, and the lowest concentration giving a total imprecision (CV) of 10% was 0.060 microg/L. The mean difference (95% limits of agreement) between the new cTnI and Aio cTnI assays was larger in admission samples (21.0%; -107.8% to 149.7%) than in samples taken 6-12 h (12.8%; -61.5% to 87.2%) and 24 h after admission (3.0%; -71.3% to 77.4%; P <0.001). With the lowest concentrations giving 10% CV (0.22 microg/L for Aio cTnI) used as cutoffs, 14.3% (n = 76) of admission samples were positive only with the new assay, whereas 13.5% (n = 72) were positive with both assays. Of samples taken at 6-12 and 24 h, 10.2% (n = 31) and 8.3% (n = 29) were positive only with the new assay. ROC curve analysis of admission samples showed a significantly higher area under the curve for the new cTnI assay (0.940) than for the Aio cTnI assay (0.846; P <0.001). The new cTnI assay gave generally lower results than the AccuTnI assay; the mean (95% limits of agreement) differences were -58.9% (-151.8% to 34.0%) in admission samples. In samples with severe interference from autoantibodies, median ratios between the new assay and AccuTnI were higher than in samples with no apparent troponin autoantibodies (0.875 vs 0.481; P<0.001). CONCLUSIONS: The new cTnI assay, which is based on a novel antibody combination different from the conventional midfragment antibody approach, offers improved detection of cTnI in samples containing troponin autoantibodies.
Susann Eriksson; Tuomo Ilva; Charlotte Becker; Juha Lund; Pekka Porela; Kari Pulkki; Liisa-Maria Voipio-Pulkki; Kim Pettersson
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, Non-U.S. Gov't     Date:  2005-02-17
Journal Detail:
Title:  Clinical chemistry     Volume:  51     ISSN:  0009-9147     ISO Abbreviation:  Clin. Chem.     Publication Date:  2005 May 
Date Detail:
Created Date:  2005-04-27     Completed Date:  2005-06-07     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  9421549     Medline TA:  Clin Chem     Country:  United States    
Other Details:
Languages:  eng     Pagination:  848-55     Citation Subset:  IM    
Department of Biotechnology, University of Turku, Turku, Finland.
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MeSH Terms
Autoantibodies / blood*
Chest Pain / diagnosis
False Negative Reactions
Myocardial Infarction / diagnosis
ROC Curve
Sensitivity and Specificity
Troponin I / blood*,  immunology*
Reg. No./Substance:
0/Autoantibodies; 0/Epitopes; 0/Troponin I
Comment In:
Clin Chem. 2005 May;51(5):803-4   [PMID:  15855663 ]

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