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. 2012 Mar 15:344:e1533.
doi: 10.1136/bmj.e1533.

Implications of lowering threshold of plasma troponin concentration in diagnosis of myocardial infarction: cohort study

Nicholas L Mills  1 , Kuan Ken Lee, David A McAllister, Antonia M D Churchhouse, Margaret MacLeod, Mary Stoddart, Simon Walker, Martin A Denvir, Keith A A Fox, David E Newby
Affiliations

Implications of lowering threshold of plasma troponin concentration in diagnosis of myocardial infarction: cohort study

Nicholas L Mills et al. BMJ. .

Abstract

Objective: To assess the relation between troponin concentration, assay precision, and clinical outcomes in patients with suspected acute coronary syndrome.

Design: Cohort study.

Setting: Tertiary centre in Scotland.

Participants: 2092 consecutive patients admitted with suspected acute coronary syndrome were stratified with a sensitive troponin I assay into three groups (<0.012, 0.012-0.049, and ≥0.050 µg/L) based on the 99th centile for troponin concentration (0.012 µg/L; coefficient of variation 20.8%) and the diagnostic threshold (0.050 µg/L; 7.2%).

Main outcome measure: One year survival without events (recurrent myocardial infarction, death) in patients grouped by troponin concentration.

Results: Troponin I concentrations were <0.012 µg/L in 988 patients (47%), 0.012-0.049 µg/L in 352 patients (17%), and ≥0.050 µg/L in 752 patients (36%). Adoption of the 99th centile would increase the number of people receiving a diagnosis of myocardial infarction from 752 to 1104: a relative increase of 47%. At one year, patients with troponin concentrations of 0.012-0.049 µg/L were more likely to be dead or readmitted with recurrent myocardial infarction than those with troponin concentrations <0.012 µg/L (13% v 3%, P<0.001; odds ratio 4.7, 95% confidence interval 2.9 to 7.9). Compared with troponin ≥0.050 µg/L, patients with troponin 0.012-0.049 µg/L had a higher risk profile but were less likely to have a diagnosis of, or be investigated and treated for, acute coronary syndrome.

Conclusion: Lowering the diagnostic threshold to the 99th centile and accepting greater assay imprecision would identify more patients with acute coronary syndrome at risk of recurrent myocardial infarction and death but would increase the diagnosis of myocardial infarction by 47%. It remains to be established whether reclassification of these patients and treatment for myocardial infarction would improve outcome.

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Conflict of interest statement

Competing interests: All authors have completed the ICMJE uniform disclosure form at www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declare: no support from any organisation for the submitted work; NLM and SW have specified relationships with Abbott Diagnostics that might have an interest in the submitted work in the previous three years.

Figures

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Fig 1 Survival free from death or recurrent myocardial infarction in patients with suspected acute coronary syndrome stratified by plasma troponin concentration
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Fig 2 Association between plasma troponin concentration and odds of death or recurrent myocardial infarction. Estimates obtained from generalised additive model with cubic smoothing spline (df=3, P=0.005 for non-linearity). Rug plot shows density of data for given value of troponin
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Fig 3 Odds of death or recurrent myocardial infarction in patients stratified by plasma troponin concentration
See this image and copyright information in PMC

Comment in

References

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