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True 99th centile of high sensitivity cardiac troponin for hospital patients: prospective, observational cohort study

BMJ 2019; 364 doi: https://doi.org/10.1136/bmj.l729 (Published 13 March 2019) Cite this as: BMJ 2019;364:l729

The use of troponin in clinical practice

Mariathas et al investigated the distribution of high sensitivity cardiac troponin I concentrations in 20000 consecutive patients undergoing a blood test for any clinical reason at a UK hospital [1]. The results showed that one in 20 (5.4%, n=1080) had a high sensitivity cardiac troponin I greater than the recommended upper limit of normal. There was no clinical suspicion of acute myocardial infarction for most of these patients. Advancing age, male sex, decreasing estimated glomerular filtration rate, and inpatient location (vs. outpatient department) were independent predictors of a patient having a high sensitivity cardiac troponin I concentration greater than the recommended upper limit of normal. These results suggest that using a threshold value of upper limit of normal to diagnosis acute myocardial infarction is less specific.

Actually, previous studies and expert consensus already pointed out that elevated troponin in itself does not indicate acute myocardial infarction because it can be caused by varied factors and conditions [2, 3]. The statistical issue of pre-test probability should be considered when interpreting the result of elevated troponin. This means the diagnosis of myocardial infarction using troponin levels should be in the context of the pre-test probability of acute coronary syndrome. Factors associated with a high pre-test probability of acute coronary syndrome including typical symptoms, ischemic ECG changes or wall-motion abnormalities on echocardiography, and the presence of coronary artery disease risk factors or history of coronary artery disease. Even with an elevated troponin, the post-test probability for acute coronary syndrome is still low in a patient with low pre-test probability of acute coronary syndrome. Therefore, it was recommended that the testing of troponin should be performed only if clinically indicated for suspected myocardial infarction [3].

However, there is actually a dilemma in the clinical practice for many doctors in China. Although many Chinese doctors know that it is not specific for myocardial infarction, the testing of troponin is still widely ordered by them, especially in wards such as intensive care units. Due to the unfriendly doctor-patient relationship in China [4], doctors are afraid of missing a diagnosis, which leads to many unnecessary subsequent tests. We hope that this dilemma will be resolved in the near future.

Yu-Ming Xu, Peng-Peng Niu, Bo Song. The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China.

References
1. Mariathas M, Allan R, Ramamoorthy S, et al. True 99th centile of high sensitivity cardiac troponin for hospital patients: prospective, observational cohort study. BMJ. 2019 Mar 13;364:l729. doi: 10.1136/bmj.l729.
2. Eggers KM, Lind L, Venge P, Lindahl B. Factors influencing the 99th percentile of cardiac troponin I evaluated in community-dwelling individuals at 70 and 75 years of age. Clin Chem. 2013 Jul;59(7):1068-73. doi: 10.1373/clinchem.2012.196634.
3. Newby LK, Jesse RL, Babb JD, et al. ACCF 2012 expert consensus document on practical clinical considerations in the interpretation of troponin elevations: a report of the American College of Cardiology Foundation task force on Clinical Expert Consensus Documents. J Am Coll Cardiol. 2012 Dec 11;60(23):2427-63. doi: 10.1016/j.jacc.2012.08.969.
4. Jie L. New generations of Chinese doctors face crisis. Lancet. 2012 May 19;379(9829):1878. doi: 10.1016/S0140-6736(12)60774-0.

Competing interests: No competing interests

15 March 2019
Xu Yu-Ming
researcher
Peng-Peng Niu, Bo Song.
The First Affiliated Hospital of Zhengzhou University
Zhengzhou, China.