False-Positive AxSYM Cardiac Troponin I Results in a 53-Year-Old Woman

2002 ◽  
Vol 126 (5) ◽  
pp. 606-609
Author(s):  
Ronald J. Knoblock ◽  
Christopher M. Lehman ◽  
Ruth A. Smith ◽  
Fred S. Apple ◽  
William L. Roberts
Keyword(s):  
Polyethylene Glycol ◽  
Rheumatoid Factor ◽  
Cardiac Troponin ◽  
Troponin I ◽  
Protein A ◽  
Cardiac Troponin I ◽  
Heterophile Antibody ◽  
Clinically Significant ◽  
Polyethylene Glycol Precipitation ◽  
Number Of Classes

Abstract A number of classes of endogenous antibodies, including heterophile, rheumatoid factor, and autoantibodies, can interfere with immunoassay measurements of many different analytes. Heterophile and rheumatoid factor antibody interferences have been described previously for the AxSYM cardiac troponin I assay. Several commercial products have been developed to neutralize heterophile antibody interferences. We describe a patient with multiple apparently falsely elevated cardiac troponin I results that were unique to the AxSYM analyzer. These cardiac troponin I results diluted linearly. When treated with 2 different heterophile-blocking reagents, the magnitudes of the falsely elevated results increased 17- and 26-fold, and these results also demonstrated dilution linearity. This interfering substance could be removed by passage through an immobilized protein A column and by polyethylene glycol precipitation. It does not appear to be a classic heterophile antibody, nor is it a paraprotein. Laboratorians must remain constantly vigilant for immunoassay interferences that lead to clinically significant inaccurate results and must recognize that accepted methods for detecting and neutralizing the interference may be ineffective.

scholarly journals Proteolytic Digestion of Serum Cardiac Troponin I as Marker of Ischemic Severity

2018 ◽  
Vol 3 (3) ◽  
pp. 450-455 ◽  
Author(s):  
Somaya Zahran ◽  
Vivian P Figueiredo ◽  
Michelle M Graham ◽  
Richard Schulz ◽  
Peter M Hwang
Keyword(s):  
Cardiac Troponin ◽  
Troponin I ◽  
Thrombus Formation ◽  
Cardiac Troponin I ◽  
Total Serum ◽  
Proteolytic Degradation ◽  
Troponin Level ◽  
Proteolytic Digestion ◽  
Severity Of Injury ◽  
Clinically Significant

Abstract Background The serum troponin assay is the biochemical gold standard for detecting myocardial infarction (MI). A major diagnostic issue is that some believe troponin levels can rise with reversible injury, in the absence of radiologically detectable infarct. Hypothesis Because cell death activates intracellular proteases, troponin released by irreversible infarct will be more proteolyzed than that released by milder processes. Our goal was to quantify proteolytic digestion of cardiac troponin I in patients with varying degrees of myocardial injury. Methods Serum or plasma samples from 29 patients with cardiac troponin I elevations were analyzed for proteolytic degradation, using 3 different sandwich ELISAs designed to specifically detect the N-terminal, core, or C-terminal regions of cardiac troponin I. Results As predicted, the degree of proteolytic digestion increased with increasing severity of injury, as estimated by the total troponin level, and this trend was more pronounced for C-terminal (vs N-terminal) degradation. The highest degree of proteolytic digestion was observed in patients with ST-elevation MI; the least, in type 2 MI (supply–demand ischemia rather than acute thrombus formation). Conclusions The proteolytic degradation pattern of cardiac troponin I may be a better indicator of clinically significant MI than total serum troponin level. Distinguishing between intact and degraded forms of troponin may be useful for (a) identifying those patients with clinically significant infarct in need of revascularization, (b) monitoring intracellular proteolysis as a possible target for therapeutic intervention, and (c) providing an impetus for standardizing the epitopes used in the troponin I assay.

scholarly journals Evaluation of Innotrac Aio! Second-Generation Cardiac Troponin I Assay: The Main Characteristics for Routine Clinical Use

2006 ◽  
Vol 2006 ◽  
pp. 1-7 ◽  
Author(s):  
P. Hedberg ◽  
J. Valkama ◽  
E. Suvanto ◽  
S. Pikkujämsä ◽  
K. Ylitalo ◽  
...  
Keyword(s):  
Rheumatoid Factor ◽  
Whole Blood ◽  
Cardiac Troponin ◽  
First Generation ◽  
Second Generation ◽  
Troponin I ◽  
Reference Group ◽  
Rapid Test ◽  
Cardiac Troponin I ◽  
The Stability

The availability of a simple, sensitive, and rapid test using whole blood to facilitate processing and to reduce the turnaround time could improve the management of patients presenting with chest pain. The aim of this study was an evaluation of the Innotrac Aio! second-generation cardiac troponin I (cTnI) assay. The Innotrac Aio! second-generation cTnI assay was compared with the Abbott AxSYM first-generation cTnI, Beckman Access AccuTnI, and Innotrac Aio! first-generation cTnI assays. We studied serum samples from 15 patients with positive rheumatoid factor but with no indication of myocardial infarction (MI). Additionally, the stability of the sample with different matrices and the influence of hemodialysis on the cTnI concentration were evaluated. Within-assay CVs were 3.2%–10.9%, and between-assay precision ranged from 4.0% to 17.2% for cTnI. The functional sensitivity(CV=20%)and the concentration giving CV of 10% were approximated to be 0.02 and 0.04, respectively. The assay was found to be linear within the tested range of 0.063–111.6μg/L. The correlations between the second-generation Innotrac Aio!, Access, and AxSYM cTnI assays were good (rcoefficients 0.947–0.966), but involved differences in the measured concentrations, and the biases were highest with cTnI at low concentrations. The second-generation Innotrac Aio! cTnI assay was found to be superior to the first-generation assay with regard to precision in the low concentration range. The stability of the cTnI level was best in the serum, lithium-heparin plasma, and lithium-heparin whole blood samples (n=10, decrease<10%in 24 hours at+20°Cand at+4°C. There was no remarkable influence of hemodialysis on the cTnI release. False-positive cTnI values occurred in the presence of very high rheumatoid factor values, that is, over 3000 U/L. The 99th percentile of the apparently healthy reference group was≤0.03 μg/L. The results demonstrate the very good analytical performance of the second-generation Innotrac Aio! cTnI assay.

Effect of seropositive rheumatoid factor on cardiac troponin I measurement using the Access® Immunoassay Analyzer

2006 ◽  
Vol 44 (10) ◽  
Author(s):  
Tze-Kiong Er ◽  
Li-Yu Tsai ◽  
Yuh-Jyh Jong ◽  
Chen-Fen Feng ◽  
Yin-Fen Tsai ◽  
...  
Keyword(s):  
Rheumatoid Factor ◽  
Cardiac Troponin ◽  
Troponin I ◽  
Cardiac Troponin I

scholarly journals Discrepancy between Cardiac Troponin Assays Due to Endogenous Antibodies

2020 ◽  
Vol 66 (3) ◽  
pp. 445-454 ◽  
Author(s):  
Leo Lam ◽  
Lisa Aspin ◽  
Robert Campbell Heron ◽  
Leah Ha ◽  
Campbell Kyle
Keyword(s):  
Regression Analysis ◽  
Polyethylene Glycol ◽  
Cardiac Troponin ◽  
Protein A ◽  
Gel Filtration ◽  
Interquartile Range ◽  
Clinical Use ◽  
Gel Filtration Chromatography ◽  
Polyethylene Glycol Precipitation

Abstract Background Despite well-described analytical effects of autoantibodies against cardiac troponin (cTn) I on experimental assays, no study has systematically examined their impact on cTn assays in clinical use. We determined the effects of endogenous antibodies on 5 different cTnI assays and a cTnT assay. Methods cTn was measured by 6 methods: Siemens hs-cTnI Centaur, Siemens hs-cTnI Vista, Abbott hs-cTnI Architect, Beckman hs-cTnI Access, Beckman cTnI Access, and Roche hs-cTnT Elecsys. Measurements were repeated on 5 assays (all except Siemens hs-cTnI Vista) following immunoglobulin depletion by incubation with protein A. Low recovery of cTnI (&lt;40%) following immunoglobulin depletion was considered positive for macro-cTnI. Protein A findings were validated by gel filtration chromatography and polyethylene glycol precipitation. Results In a sample of 223 specimens selected from a community laboratory that uses the Siemens hs-cTnI Centaur assay and from which cTn was requested, 76% of samples demonstrated increased cTnI (median, 88 ng/L; interquartile range, 62–204 ng/L). Macro-cTnI was observed in 123 (55%) of the 223 specimens. Comparisons of cTnI assays markedly improved once patients with macro-cTnI were removed. Passing-Bablok regression analysis between hs-cTnI assays demonstrated different slopes for patients with and without macro-cTnI. In patients with macro-cTnI, 89 (72%) showed no effect on the recovery of cTnT, whereas 34 (28%) had reduced recovery of cTnT. The proportion of results above the manufacturers' 99th percentile varied with the cTn assay and macro-cTnI status. Conclusion We suggest that the observed discrepancy between hs-cTnI assays may be attributed in part to the presence of macro-cTnI.

High percentage of false positive cardiac troponin I results in patients with rheumatoid factor

1999 ◽  
Vol 32 (6) ◽  
pp. 477-480 ◽  
Author(s):  
John Krahn ◽  
David M Parry ◽  
Michael Leroux ◽  
James Dalton
Keyword(s):  
Rheumatoid Factor ◽  
False Positive ◽  
Cardiac Troponin ◽  
Troponin I ◽  
Cardiac Troponin I
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