MedicalResearch.com Interview with:
Martin P. Than, MBBS
Emergency Department, Christchurch Hospital and
Dr John W Pickering, PhD
Associate Professor Senior Research Fellow in Acute Care
Emergency Care Foundation, Canterbury Medical Research Foundation, Canterbury District Health Board | Christchurch Hospital
Research Associate Professor | Department of Medicine | University of Otago
Christchurch New Zealand
MedicalResearch.com: What is the background for this study?
Response: Patients being investigated for possible acute coronary syndrome comprise one of the largest groups of patients presenting to emergency rooms. Troponin assays have developed such that they can now measure with greater accuracy much lower concentrations of troponin. A large retrospective registry based study and a couple of smaller prospective studies suggested that patients with a very low concentrations of troponin T (below the current limit of detection of 5 ng/L) measured with Roche Diagnostic’s high-sensitivity troponin T (hsTnT) assay on presentation to the emergency department (ie single blood draw) are very unlikely to be having a myocardial infarction (MI).
Our study gathers the current best evidence for using concentrations below the limit of detection in conjunction with no evidence of new ischaemia on ECG to safely risk stratify patients to a very low-risk group for MI and, therefore, potentially identify patients safe for early discharge.
MedicalResearch.com: What are the main findings?
Response: We searched the literature and contacted authors of prospective studies that appeared to have the necessary data. In the end eleven studies participated comprising 9241 patients who were investigated for potential ACS. Thirty percent of these patients (2825) had hsTnT concentrations below the limit detection and no evidence of ischaemia. Of these 14 had an Myocardial Infarction (the False Negatives). The pooled estimate of sensitivity was 98.7% (95% confidence interval 96.6% to 99.5%). Some individual studies had lower sensitivity. Of the 14 FNs, 7 were in patients in whom the blood draw was within 3 hours of symptom onset.
MedicalResearch.com: What should readers take away from your report?
Response: A single blood draw and use of the hsTnT assay can be used to risk stratify a substantial portion of patients to a low-risk category. We recommend for maximum safety that this strategy only be used with patients more than 3 hours from symptom onset and that local audits be used to double check safety and efficacy in individual hospitals.
As we noted in the paper, this strategy is not intended to risk-stratify patients to a high-risk category. ie it is only an early screening test to identify a very low-risk group.
MedicalResearch.com: What recommendations do you have for future research as a result of this study?
Response: Readers may be interested that in New Zealand several emergency departments currently use serial measurements of hsTnT two or three hours apart along with ECG and a risk assessment score (EDACS or TIMI) to risk stratify patients early. We hope to investigate in a clinical (rather than research) setting the added value of using the single blood draw strategy described in this current report to risk-stratify even earlier.
MedicalResearch.com: Is there anything else you would like to add?
Response: Roche diagnostics played no part in this study, although we note in the supplement that several of the component studies had previously received support for the assay measurement from the company.
MedicalResearch.com: Thank you for your contribution to the MedicalResearch.com community.
Pickering JW, Than MP, Cullen L, Aldous S, ter Avest E, Body R, et al. Rapid Rule-out of Acute Myocardial Infarction With a Single High-Sensitivity Cardiac Troponin T Measurement Below the Limit of Detection: A Collaborative Meta-analysis. Ann Intern Med. [Epub ahead of print 18 April 2017] doi: 10.7326/M16-2562
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