Multicenter Comparison of Four Contemporary Sensitive Troponin Immunoassays

Background: The IFCC Task Force on Clinical Applications of Cardiac Biomarkers currently recommends evaluation of all troponin immunoassays within the same population to compare their performance. Hence, we planned a multicenter study to compare the four most widespread contemporary sensitive troponin I (TnI) methods. Methods: Seventy-six serum samples were centrifuged, separated and divided in 5 aliquots. The first aliquot was used for clinical measurement, whereas the rest were shipped to participating laboratories, where they were simultaneously thawed. High-sensitivity troponin T (HS-TnT) was measured on a Roche Cobas, whereas TnI was assessed with the Ortho Vitros cTnI, Beckman Coulter DXI 800 AccuTnI, Siemens Vista cTnI and Abbott Architect STAT cTnI. Results: A substantial bias was found between TnI and HSTnT values. Although the correlation was acceptable and comprised between 0.86-0.89, the agreement of diagnostic values was poor, with the kappa statistic always lower than 0.50. Although the direct comparison between the four contemporary sensitive TnI immunoassays generated more favourable results, with Pearson’s correlations greater than 0.970 and the kappa statistic equal to or higher than 0.59, we observed wide 95% confidence intervals, significant bias and large dispersion of values, with a single notable exception (i.e., Vitros cTnI versus DXI 800 AccuTnI). Conclusions: The results of this study attest that substantial discrepancies still exist among contemporary sensitive TnI immunoassays. The presence of random variation rather than constant bias appears to be the major contributor to this variance, thus precluding the interchangeability of methods and making the objective of harmonization a rather long and challenging enterprise.