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Three Part Question

In [patient with cardiac chest pain] can [point of care cardiac triple marker at 120 minutes]rule out[Acute Coronary Syndrome (ACS) reliably]

Clinical Scenario

A fifty year male attends Emergency Department (ED) with cardiac sounding chest pain 2 hours ago and the pain lasted for 30 minutes. Now he is pain free and there is no history of previous IHD. He is ex smoker but has no other risk factors for IHD. His ECG is completely normal. You wonder if Point of Care (POC) triple markers can be requested 2-3 hours after the onset of pain in such cases and ACS can be realibly ruled out to allow safe discharge from ED.

Search Strategy

We searched MEDLINE 1946 to January 2012 and EMBASE 1980-2011 using Ovid interface. We also searched Cochrane Database of Systemic Reviews on 1st of February 2012: (Myocardial Ischemia/ OR Angina, Unstable/ OR Myocardial Infarction/ OR non ST elevation MI.mp. OR Acute Coronary Syndrome/) AND
(exp Enzyme Assays/)AND
(exp Point-of-Care Systems/)AND
(Emergency Medicine/ or Emergency Service, Hospital/)
1 and 2 and 3 and 4
1 and 3 and 4

Search Outcome

Forty four papers were identified by searching the data bases, of which 3 were relevant.

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Diercks et al 2012 USA	Convenient sample of 858 adult patients with cardiac chest pain for at least 30 minutes and within 8 hours	Prospective blinded observational cohort multicentre study	sensitivity, specificity, positive, negative predictive value of POC cardio3 TnI at 90, 180 and 360 minutes	93.4% of STEMI & NSTEMI patients had elevated cardio3 TnI value before or at 3 hours from presentation. The sensitivity, specificity, positive & negative likelihood ratios were 84.1, 93.4, 12.8 and 0.17 respectively. Adding 6 hours serial testing to 3 hours sample did not improve diagnostic accuracy significantly	Spectrum bias for enrolled patient and Inclusion bias of sample to early presenters, therefore, possibly of benefits can not be excluded for patients presenting immediately after onset of symptoms. No direct comparison was made with other biomarker strategies.
Than M at el March 23, 2011 New Zealand	3582 adult patients with cardiac chest pain for at least 5 minutes duration	Prospective observational study in 14 EDs of 9 countries in the Asia-Pacific region. POC biomarkers were measured at presentation and 2 hours afterwards for Top I, CK MB and Myoglobin.	The primary endpoint was major adverse cardiac events within 30 days after initial presentation	Accelerated Diagnostic Protocol ( ADP); Use of TIMI, ECG, POC biomarkers; classified 9.8% of patients as low risk; 0.9% of these patients had an event during initial hospital attendance and follow-up. ADP was 99.3% sensitive with 99.1% NPV.	Observational study with low (11%) specificity. There is no universally accepted definition of low risk patients for acute coronary syndrome.

Comment(s)

Although all three trials favour safe use of point of care tests at 90-180 minutes, Than et al study suggested that high sensitivity and negative predictive value is better achieved by adding accelerated diagnostic protocol that relied on low risk group with 0 TIMI score and normal ECGs. Diercks et al pointed out that adding 6 hours serial testing did not add diagnostic accuracy significantly.

Clinical Bottom Line

Limited high quality evidence suggests that point of care cardiac markers may be used safely as early as 90-120 minutes for safe decision making in patients with low risk cardiac chest pain.

References

1. Diercks DB, Peacock WF, Hollander JE et al Diagnostic accuracy of a point of care troponin I assays for acute myocardial infarction within 3 hours after presentation in early presenters to the emergency department with chest pain Am Heart J 2012; 163: 74-80
2. Goodacre SW, Bradburn M, Cross E et al The randomised assessment of treatment using panel assay of cardiac markers (RATPAC) trial: A randomised controlled trial of point of care cardiac markers in the emergency department Heart 2011; 190-196
3. Than M, Cullen L, Reid CM et al A 2-h diagnostic protocol to assess patients with chest pain symptoms in the Asia-Pacific region (ASPECT): A propective observational validation study Lancet 2011; 377: 1077-84