Over the next few months Western Diagnostic Pathology will introduce the latest 5th generation hs-cTnI assay from Beckman. This assay demonstrates superior analytical, diagnostic and prognostic performance over contemporary cTn assays (4th generation). The new hs-cTnI has less analytical variability, <10% variability at the 99th centile upper reference limit (URL), and an ability to accurately measure very low levels of troponin, as low as 2 ng/L. As a result of improved performance there will be a corresponding change in reporting units and reference intervals (including adoption of gender specific reference intervals).
Gender Specific Reference Interval for Beckman hs-cTnI
Western Diagnostic Pathology will be changing our reporting units as the new hs-cTnI (Beckman) is rolled out across WA and NT. Current (4th generation) troponin assays in WA report in ug/L, which will change to ng/L with the introduction of 5th generation (hs-cTnI) troponin assay, which will better reflect the analytical sensitivity of the new assay.
Troponin plays an important role in the evaluation of patients with suspected acute myocardial infarction.
Fourth Universal Definition of Myocardial Infarction states that a diagnosis of myocardial infarction is made when there is a rise and/or fall of troponin with at least one value above the 99th centile URL and at least one of the following: typical symptoms of ischemia, suggestive electrocardiographic (ECG) changes, or imaging evidence of new loss of viable myocardium or new regional wall motion abnormality.
Troponin may be elevated in the absence of an acute event. In these (general population) patients, the typical rise and fall of troponin with an ischemic event will not be seen.
Causes of elevated troponin
Strong consideration should be given to referring patients to attend an emergency department for clinical assessment where:
- Patient presenting with suspected acute coronary syndrome with symptoms occurring within the previous 24 hours or
- Patients with suspected acute coronary syndrome and symptoms >24 hours prior to high-risk features (heart failure, syncope, abnormal ECG).
Careful consideration should be given when requesting a troponin on an outpatient basis, as this might delay a timely diagnosis and management of an acute coronary syndrome.
However, a single troponin may be indicated (community-based) in patients presenting with a history of a possible acute coronary syndrome within the past 14 days (but only if symptom-free for more than 24 hours with no high-risk features) . It is important the requesting doctor ensures the sample is clearly marked as urgent, with a robust communication system in place to facilitate the laboratory relaying the result to requesting doctor as soon as possible.
References:
Carlton, E., Cullen, L. and Body, R., 2017. Appropriate Use of High-Sensitivity Cardiac Troponin Levels in Patients With Suspected Acute Myocardial Infarction—Reply. JAMA Cardiology, 2(2), p.229.
Greenslade, J., Carlton, E., Van Hise, C., Cho, E., Hawkins, T., Parsonage, W., Tate, J., Ungerer, J. and Cullen, L., 2018. Diagnostic Accuracy of a New High-Sensitivity Troponin I Assay and Five Accelerated Diagnostic Pathways for Ruling Out Acute Myocardial Infarction and Acute Coronary Syndrome. Annals of Emergency Medicine, 71(4), pp.439-451.e3.
Marshall, G., Wijeratne, N. and Thomas, D., 2014. Should general practitioners order troponin tests?. The Medical Journal of Australia, 201(3), pp.155-157.
Thygesen, K., Alpert, J., Morrow, D., White, H., Jaffe, A., Chaitman, B. and Bax, J., 2018. Fourth universal definition of myocardial infarction (2018). [online] European Heart Journal. Available at: <https://academic.oup.com/eurheartj/advance-article/doi/10.1093/eurheartj/ehy462/5079081> [Accessed 16 Oct. 2018].
Twerenbold, R., Boeddinghaus, J., Nestelberger, T., Wildi, K., Rubini Gimenez, M., Badertscher, P. and Mueller, C., 2017. Clinical Use of High-Sensitivity Cardiac Troponin in Patients With Suspected Myocardial Infarction. Journal of the American College of Cardiology, 70(8), pp.996-1012
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