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Original article
Direct comparison of clinical decision limits for cardiac troponin T and I
  1. Dorien M Kimenai1,2,
  2. Ronald MA Henry2,3,
  3. Carla JH van der Kallen2,3,
  4. Pieter C Dagnelie2,4,5,
  5. Miranda T Schram2,3,
  6. Coen DA Stehouwer2,3,5,
  7. Jeroen DE van Suijlen6,
  8. Marijke Niens6,
  9. Otto Bekers1,2,
  10. Simone JS Sep2,3,
  11. Nicolaas C Schaper2,3,5,
  12. Marja P van Dieijen-Visser1,2,
  13. Steven JR Meex1,2
  1. 1Department of Clinical Chemistry, Maastricht University Medical Centre (MUMC+), Maastricht, The Netherlands
  2. 2Cardiovascular Research Institute Maastricht (CARIM), Maastricht University, Maastricht, The Netherlands
  3. 3Department of Medicine, MUMC+, Maastricht, The Netherlands
  4. 4Department of Epidemiology, MUMC+, Maastricht, The Netherlands
  5. 5School for Public Health and Primary Care (CAPHRI), Maastricht University, Maastricht, The Netherlands
  6. 6Department of Clinical Chemistry, Gelre Hospital, Apeldoorn, The Netherlands
  1. Correspondence to Steven JR Meex, Department of Clinical Chemistry, Maastricht University Medical Centre (MUMC+), PO Box 5800, Maastricht 6202 AZ, The Netherlands; steven.meex{at}mumc.nl

Abstract

Objective The 99th percentile upper reference limit of high-sensitivity cardiac troponin (hs-cTn) from a healthy reference population is used for diagnosing acute myocardial infarction (AMI). Accepted current thresholds of hs-cTnT (Roche) and hs-cTnI (Abbott) are 14 and 26 ng/L, respectively. Since thresholds for hs-cTnT and hs-cTnI were derived from different reference cohorts it is unclear whether they are biologically equivalent. We directly assessed sex-specific and age-specific 99th percentile upper reference limits of hs-cTnT and hs-cTnI in a single reference cohort, to investigate whether current divergent thresholds of hs-cTnT and hs-cTnI stem from intrinsic assay differences or reflect cohort variation.

Methods A healthy reference population was derived from a population-based cohort (the Maastricht Study: n=3451; age: 40–75 years). Individuals with diabetes mellitus, a history of cardiovascular disease, cardiac ischaemia on ECG, N-terminal pro-brain natriuretic peptide >125 ng/L or estimated glomerular filtration rate <60 mL/min/1.73 m2 were excluded. Non-parametric analyses were performed to assess 99th percentile upper reference limits.

Results 1540 individuals were included in the healthy reference population (age 57±8 years, 52.4% women). Overall 99th percentile upper reference limits of hs-cTnT and hs-cTnI were 15 and 13 ng/L, respectively. Upper reference limits were higher in men than women (hs-cTnT: 16 vs 12 ng/L), (hs-cTnI: 20 vs 11 ng/L) and increased with age.

Conclusions Direct comparison reveals numerically similar thresholds for hs-cTnT and hs-cTnI assays. This finding is in line with recently reported underdiagnosis of AMI with the current decision limit of 26 ng/L for hs-cTnI, especially among women. Downwards adjustment of the hs-cTnI threshold, differentiated for sex, would equalise clinical decision limits for both assays, and may prevent further underdiagnosis of AMI.

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