Annals of Clinical & Laboratory Science 35:453-454 (2005)
© 2005 Association of Clinical Scientists
Comparison of Cardiac Troponin I Levels in Serum and Sodium-Citrate Plasma Using the ACCESS 2 Immunoassay
Yu-Sin Wang1,
Chen-Fen Feng1,
Tze-Kiong Er1,
Li-Yu Tsai1,
Chian-Yu Chen1,
Shun-Jen Chang2 and
Bai-Hsiun Chen1
1 Department of Laboratory Medicine, Kaohsiung Medical University Hospital, and 2 Department of Public Health, Kaohsiung Medical University, Kaohsiung, Taiwan.
Address correspondence to Bai-Hsiun Chen, M.D., Department of Laboratory Medicine, Kaohsiung Medical University Hospital, 100 Shih-Chuan 1st Rd., Kaohsiung, Taiwan; tel 886 7 312 1101, x7231; fax: 886 7-311 4449; e-mail chen_bh. tw{at}yahoo.com.tw.
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Abstract
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The aim of this study was to determine if sodium-citrate plasma is a suitable substitute for serum for cardiac troponin I (cTnI) measurement using the Beckman ACCESS 2 immunoassay. Linear regression analysis of cTnI levels in paired serum and sodium-citrate plasma samples from 80 patients provided a y-intercept of –0.0193 and a slope of 1.044. The correlation was good [r = 0.995; 95% confidence interval 1.017 to 1.068, p <0.0001]. The paired results were not significantly different by Student’s t-test. Serum and sodium-citrate plasma appear to be interchangeable as samples for cTnI measurement using the ACCESS 2 assay. Furthermore, the use of plasma reduces the turnaround time and may avoid false positive cTnI results due to residual fibrin.
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Introduction
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The measurement of troponins in blood has rapidly become an accepted method of detecting myocardial damage [1,2]. Furthermore, the recently redefined criteria for myocardial infarction that are used to classify patients with acute coronary syndrome have been established on the basis of increased serum/plasma concentrations of cTnI or cTnT [3]. Studies have indicated the prognostic importance of increased troponins in various clinical settings [4,5]. For determination of cardiac troponins, many laboratories prefer plasma rather than serum. Serum and heparin-plasma samples have been reported to be suitable for cTnI determination by the ACCESS 2 immunoassay [6], but not sodium-citrate plasma. The aim of this study was to determine if sodium-citrate plasma is suitable for cTnI tests using the ACCESS 2 immunoassay.
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Materials and Methods
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We collected randomly 2 series of 80 blood samples from patients admitted to our hospital. For each patient, a serum (BD Vacutainer clot tube) and a plasma specimen (BD Vacutainer 3.2% sodium citrate tube) were obtained. cTnI was measured by Beckman ACCESS 2 analyzer. To determine the assay imprecision, we selected 2 samples with high and low concentrations of cTnI in our study group. Both samples were analyzed in triplicate; the CV’s were 2.90% and 2.12 %, respectively.
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Results
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Linear regression analysis of cTnI levels in paired serum and plasma samples from 80 patients provided a y-intercept of –0.0193 and a slope of 1.044 (Fig. 1
). The correlation was good [r = 0.995; 95% confidence interval 1.017 to 1.068, p <0.0001]. Results for serum ranged from 0 to 29.92 ng/ml (mean: 1.604 ng/ml) and for plasma ranged from 0 to 27.11 ng/ml (mean: 1.655 ng/ml). The paired results were not significantly different by Student’s t-test. No sample dilution effect was observed with sodium citrate plasma.
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Fig. 1. Comparison of cTnI concentrations in 80 paired samples of serum and sodium citrate plasma yielded a correlation coefficient (r) of 0.995 (see text).
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Discussion
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Generally, paired blood samples (clot tube and sodium-citrate containing tube) were obtained from patients who were being evaluated in the emergency room of our hospital for acute myocardial infarction (AMI) or suspected AMI. Insufficient serum for cTnI assay was often a problem when a set of urgent tests was ordered for an emergency room patient. This situation can be managed easily, since our data show no significant difference between cTnI levels in paired serum and sodium-citrate plasma samples. Serum and sodium-citrate plasma appear to be interchangeable as samples for cTnI measurement using the ACCESS 2 assay. Furthermore, the use of plasma reduces the analytical turnaround time and may avoid false positive cTnI results due to residual fibrin.
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References
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- Adams JEI, Bodor GS, Davila-Roman VG, Delmez JA, Apple FS, Landenson JH, et al. Cardiac troponin I. A marker with high specificity for cardiac injury. Circulation 1993;88:101–106.[Abstract/Free Full Text]
- Gerhardt W, Katus H, Ravkilde J, Hamm C, Jorgensen PJ, Peheim E, et al. S-Troponin in suspected ischemic myocardial injury compared with mass and catalytic concentrations of S-creatine isoenzyme MB. Clin Chem 1991;37:1405–1411.[Abstract/Free Full Text]
- Alpert JS, Thygesen K, Antman E, Bassand JP, Klein W, Ohman M, et al. Myocardial infarction redefined–a consensus document of the Joint European Society of Cardiology/American College of Cardiology Committee for the Redefinition of Myocardial Infarction. J Am Coll Cardiol 2000; 36:959–969.[Free Full Text]
- Lindahi B, Venge P, Wallentin L. Relation between troponin T and the risk of subsequent cardiac events in unstable coronary artery disease. Circulation 1996;93: 1651–1657.[Abstract/Free Full Text]
- Lindahi B, Venge P, Wallentin L. Troponin T identifies patients with unstable coronary artery disease who benefit from long-term antithrombotic protection. J Am Coll Cardiol 1997;29:43–48.[Abstract]
- Denise UG, Wu HB, Apple FS, Jevans AW, Venge P, Olson MD, et al. Multicenter evaluation of an automated assay for troponin I. Clin Chem 2002;48:869–876.[Abstract/Free Full Text]
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Abstract
Introduction
