The impact of marker selection and process improvements on cardiac care

Although cardiac troponin I (cTnI) is now considered the marker of choice for the diagnosis of acute myocardial infarction,¹ important ongoing efforts promise to deliver further improvements to cardiac testing. Specifically, efforts are underway to simplify the use of this protein through standardization and/or harmonization.

This is vital because there are roughly 20 troponin I assays on the market all of which deliver different results. In fact, results from an identical sample can produce up to a hundredfold difference when measured with different manufacturers assays. Differences in the antibody detection system and the material used for calibration contribute to this variation. This heterogeneity among assays can create confusion among the end-users of the test the clinicians and ultimately impact the quality of patient care.

The cTnI Standardization Committee created by the American Association for Clinical Chemistry (AACC) has been reviewing and selecting troponin reference material that can be used by all manufacturers. Although this effort will not eliminate the differences among assays, it is expected to enable harmonization. Harmonization implies congruency between cTnI systems for measurements performed in the biological matrix (patient serum) such that results are coincident throughout the measurement range. The identification process involves the distribution and evaluation of candidate reference materials called round robins. Results of the first round robin were published in
2001.² A draft of a manuscript detailing the outcomes of the second round robin performed in 2002 is currently under review for future publication.

The outcome of these round robins was the committees identification and recommendation of the final product composed of a human troponin CTI complex, which consists of all three isoforms: troponin I, troponin T, and troponin C. The National Institute of Standards and Technology has conducted extensive analytical characterization studies and will be distributing the product with a planned availability in 2004.

According to the cTnI Committee Chair, Stephen Kahn, PhD, DABCC, FACB, the committee will conduct a third and final round robin in 2004. The purpose of this effort will be to enable optimization in the use of the cTnI reference material by manufacturers in the calibration of their assays.

The efforts of the AACCs cTnI Standardization Committee will be significant, helping to promote and optimize the clinical utility of troponin I as the gold standard for myocardial damage.

Linda C. Rogers, PhD, DABCC, FACB, is a medical information scientist for Beckman Coulter Inc. in Fullerton, CA.

References

1. Jaffe A, et al: Its time for a change to a troponin standard.
   Circulation. 2000;102,1216-1220.
2. Christenson RH, Duh S-H, Apple FS, Bodor GS, Bunk DM, Dalluge J, et al.; Standardization of Cardiac Troponin I Assays: Round Robin of Ten Candidate Reference Materials.
   Clin Chem. 2001;47:431-437.

January
2004: Vol. 36, No. 1©
2004 Nelson Publishing, Inc. All rights reserved.