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Canadian Journal of Cardiology

Caution When Using High-Sensitivity Cardiac Troponin I Assay to Rule Out Acute Ischemia: When the Delta to Rule In Is Within Analytical Variation

Published:March 18, 2020DOI:https://doi.org/10.1016/j.cjca.2020.03.011
      Concentration changes of 1-2 ng/L with Abbott’s high-sensitivity cardiac troponin I (hs-cTnI) assay are evident near 5 ng/L owing to acceptable variation of the assay at this low concentration.
      • Kavsak P.A.
      • Petryayeva E.
      • Clark L.
      Analytical variation and Abbott Diagnostics high-sensitivity cardiac troponin I risk categories in asymptomatic individuals.
      Accordingly, larger deltas or changes in concentrations are required to demonstrate a rise or fall in hs-cTnI, which is especially important in the acute setting where physicians are ruling in patients for possible acute myocardial infarction.
      • Wu A.H.B.
      • Christenson R.H.
      • Greene D.N.
      • et al.
      Clinical laboratory practice recommendations for the use of cardiac troponin in acute coronary syndrome: expert opinion from the Academy of the American Association for Clinical Chemistry and the Task Force on Clinical Applications of Cardiac Bio-Markers of the International Federation of Clinical Chemistry and Laboratory Medicine.
      In this regard, the latest approved hs-cTnI assay in Canada (Ortho Clinical Diagnostics; limit of quantification = 1.2 ng/L; overall 99th percentile = 11ng/L) has a published delta or change in hs-cTnI concentrations of ≥ 4 ng/L over 1 hour to rule in patients in the emergency setting.
      • Boeddinghaus J.
      • Twerenbold R.
      • Nestelberger T.
      • et al.
      Clinical use of a new high-sensitivity cardiac troponin I assay in patients with suspected myocardial infarction.
      However, a delta of 4 ng/L from > 11 ng/L (> 99th-percentile) to < 40 ng/L falls within the acceptable total error for hs-cTnI testing.
      • Wu A.H.B.
      • Christenson R.H.
      • Greene D.N.
      • et al.
      Clinical laboratory practice recommendations for the use of cardiac troponin in acute coronary syndrome: expert opinion from the Academy of the American Association for Clinical Chemistry and the Task Force on Clinical Applications of Cardiac Bio-Markers of the International Federation of Clinical Chemistry and Laboratory Medicine.
      At concentrations ≥ 40 ng/L this delta represents ≤ 10% variation with acceptable imprecision (coefficient of variation [CV]) for hs-cTnI being ≤ 10%.
      • Wu A.H.B.
      • Christenson R.H.
      • Greene D.N.
      • et al.
      Clinical laboratory practice recommendations for the use of cardiac troponin in acute coronary syndrome: expert opinion from the Academy of the American Association for Clinical Chemistry and the Task Force on Clinical Applications of Cardiac Bio-Markers of the International Federation of Clinical Chemistry and Laboratory Medicine.
      Furthermore, some commercial quality control (QC) material may yield greater imprecision estimates compared with patient material when tested daily, thereby further limiting the ability of the laboratory to truly detect suboptimal analytical performance.

      Kavsak PA, Clark L. Commercial quality control imprecision estimates for high-sensitivity cardiac troponin deltas used to rule-in myocardial infarction with the ESC 0/1 hour algorithm [epub ahead of print]. J Appl Lab Med, https://doi.org/10.1093/jalm/jfaa030.

      Accordingly, we set out to evaluate the imprecision of QC material as well as patient material within the first 100 minutes from the first result with Ortho Clinical Diagnostics’ hs-cTnI assay to assess the robustness of a 4 ng/L delta.
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      References

        • Kavsak P.A.
        • Petryayeva E.
        • Clark L.
        Analytical variation and Abbott Diagnostics high-sensitivity cardiac troponin I risk categories in asymptomatic individuals.
        Can J Cardiol. 2019; 3: 1605.e7-1605.e8
        • Wu A.H.B.
        • Christenson R.H.
        • Greene D.N.
        • et al.
        Clinical laboratory practice recommendations for the use of cardiac troponin in acute coronary syndrome: expert opinion from the Academy of the American Association for Clinical Chemistry and the Task Force on Clinical Applications of Cardiac Bio-Markers of the International Federation of Clinical Chemistry and Laboratory Medicine.
        Clin Chem. 2018; 6: 645-655
        • Boeddinghaus J.
        • Twerenbold R.
        • Nestelberger T.
        • et al.
        Clinical use of a new high-sensitivity cardiac troponin I assay in patients with suspected myocardial infarction.
        Clin Chem. 2019; 6: 1426-1436
      1. Kavsak PA, Clark L. Commercial quality control imprecision estimates for high-sensitivity cardiac troponin deltas used to rule-in myocardial infarction with the ESC 0/1 hour algorithm [epub ahead of print]. J Appl Lab Med, https://doi.org/10.1093/jalm/jfaa030.