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Serial multiple biomarkers in the assessment of suspected acute coronary syndrome: multiple infarct markers in chest pain (MIMIC) study
Emergency Medicine Journal, 04/09/2012
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Clinical Article
Macdonald SPJ et al. – Serial multiple biomarker (SMB) alone is not sufficiently sensitive to exclude myocardial infarction (MI). Combined with risk scoring, SMB appears to identify patients at lower risk. This requires prospective validation.
Methods- A prospective, multicentre, observational study enrolled patients undergoing evaluation for possible MI.
- Blood samples at presentation and 2 h later were analysed for myoglobin, creatinine kinase-MB, troponin-I and B-natriuretic peptide.
- Thrombolysis in Myocardial Infarction (TIMI) score and National Heart Foundation of Australia/Cardiac Society of Australia and New Zealand (NHF/CSANZ) guideline for acute coronary syndrome were used to determine clinical risk.
- Primary outcome was MI diagnosed at index presentation.
- Secondary outcome was composite of all-cause mortality, MI and previously unplanned coronary revascularisation within 30 days.
- 1758 patients were recruited.
- 168 (11%) of 1501 with data sufficient for analysis had MI, and 223 (14%) of 1620 had a secondary outcome.
- SMB sensitivity and specificity were 0.90 (95% CI 0.84 to 0.94) and 0.41 (95% CI 0.39 to 0.44) for MI.
- For 30-day outcome, SMB sensitivity and specificity were 0.84 (95% CI 0.78 to 0.88) and 0.41 (95% CI 0.39 to 0.44), compared with standard 8-12h troponin sensitivity and specificity of 0.79 (95% CI 0.73 to 0.84) and 0.96 (95% CI 0.95 to 0.97).
- Combined with risk scores, SMB had sensitivity and specificity for MI of 0.99 (0.96 to 1.00) and 0.11 (95% CI 0.09 to 0.12) for TIMI score 0, compared with 0.98 (95% CI 0.94 to 0.99) and 0.31 (95% CI 0.29 to 0.34) for NHF/CSANZ low/intermediate risk groups.
Stephen Macdonald (04/10/2012) comments:
Chest pain is one of the most common presenting complaints among Emergency Department (ED) patients. The majority are found not to have a serious diagnosis after assessment and can be discharged. To exclude myocardial infarction (MI) however requires testing for troponin up to 6-8 hours from pain. This means a large number remain in the ED for several hours before being found suitable to go home. This impacts on patient flow and access for new patients in the ED.
We looked at combining troponin with additional biomarkers which are elevated at earlier stage following an MI. Our aim was to exclude MI within 2 hours of ED presentation, thus potentially allowing for earlier discharge. This approach is not new but our study aimed to evaluate this in a large "real world" sample of ED patients with chest pain.
As expected the multiple biomarker approach was not as specific as troponin for MI. Overall, the sensitivity for MI was 90%. When combined with clinical risk scores (TIMI risk score and National Heart Foundation of Australia - NHF) however, the sensitivity for MI increased to over 98%. This is important since risk stratification using clinical features and ECG is an integral component of chest pain evaluation. On our results a multiple biomarker approach along with risk stratification allows exclusion of MI within 2 hours in up to 30% of ED patients presenting with chest pain. This would have significant impact on patient flow and resource use in the ED if these findings are confirmed in validation studies.