High-sensitivity cardiac troponin: do think twice, it's not all right

Evaluation of analytical performance of immunoassay methods for cTnI and cTnT: From theory to practice

Current guidelines worldwide recommend cardiac troponins I (cTnI) and T (cTnT) as the biomarkers of choice for the differential diagnosis of acute coronary syndrome (ACS), and the measurement of the 99th upper reference population limit (URL) value for cardiac troponins, with an imprecision of ≤10 CV%. Measuring the 99th URL of cTnI and cTnT is a challenging analytical task due to low biomarker concentrations present in healthy subjects. Therefore, since the year 2006, several manufacturers have established new generation cTnI and cTnT immunoassays with an improved analytical sensitivity in accordance with the quality specifications described in international guidelines, the more recent of which state that only immunoassays that meet the required quality specifications should be considered "high-sensitivity" methods. For the early diagnosis of ACS, and for the stratification of cardiovascular risk in cardiac patients and the general population, high-sensitivity methods should be employed. It is therefore important for laboratory professionals and clinicians to gain a thorough understanding of the analytical performances of immunoassay methods for cTnI and cTnT, especially at low to normal concentration ranges. The aim of the present study was to analyze critical aspects related to definition, analytical performance, pathophysiological interpretations, and the clinical relevance of high-sensitivity cardiac troponin assays.

Multi-centre evaluation of recent troponin assays for the diagnosis of NSTEMI

Objectives

We aimed to compare the use of nine different cardiac troponin (cTn) assays (2 cTnT and 7 cTnI) for the diagnosis of NSTEMI in a single multi-centre population.

Design and methods

One hundred and fifty-eight patients were included (mean age 60 years, SD 17 years), including 23 patients (14%) with NSTEMI.

Results

The analytical comparison highlighted a large heterogeneity of cTn assays, as reflected by percentages of patients with detectable cTn, correlation coefficients, Passing-Bablok comparisons and concordance coefficients. Correlations within cTnI assays were good and correlation within cTnT assays was excellent. Diagnostic performances demonstrated that each cTn assay has specific threshold values. Furthermore, some assays (HS-cTnI and T, cTnI-Pathfast and cTnI-Centaur) indicated high sensitivity and negative predictive value using the limit of detection (LoD) diagnostic strategy. For the latter assays, a significant increase in specificity was found when using the 99th percentile or the H0-H3 strategies, in comparison to the LoD strategy. When applying the European Society of Cardiology H0-H3 algorithm, comparable diagnostic performances were obtained.

Conclusion

All 9 cTn assays indicated overall good diagnostic performances for the diagnosis of NSTEMI in emergency departments when the recommended algorithm based on the variation of cTn value between two measurements at admission and 3 h later was used.

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We compare nine troponin assays for the diagnosis of NSTEMI.

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Each cTn assay owns specific thresholds for the ESC H0-H3 algorithm.

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All assays present high specificity for NSTEMI diagnosis using H0-H3 algorithm.

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Assay-specific threshold and delta change values for each cTn assays are mandatory.