Novel Protein Markers of Acute Coronary Syndrome Complications in Low-Risk Outpatients: A Systematic Review of Potential Use in the Emergency Department

Background: Published literature was systematically reviewed to determine the diagnostic accuracy of new protein markers of acute coronary syndromes (ACS) in symptomatic outpatients at low risk of ACS and related complications comparable to patients evaluated in emergency department chest pain units.Methods: Studies were identified by a MEDLINE® (1966 to May week 3, 2005) search. Abstracts were reviewed for relevance, and manuscripts were included by the independent consensus of 2 observers based on explicit criteria restricting the analysis to studies relevant to screening ambulatory patients with symptoms suggesting ACS. Publication bias was identified by a modified funnel plot analysis [study size (y) vs the inverse of the negative likelihood ratio (x)]. Results of individual markers were reported separately. When 3 or more eligible studies were identified, data were aggregated by use of the summary ROC (SROC) curve.Results: Twenty-two protein markers in 10 unique populations met the inclusion criteria. Data required for SROC analysis (true- and false-positive rates) were available for 17 markers, in 9 unique populations, from publications and personal communications. Of these, only C-reactive protein was published in more than 2 populations to allow aggregation (6 studies total). C-Reactive protein demonstrated poor diagnostic performance on SROC curve analysis, with an area under the curve of 0.61 and a pooled diagnostic odds ratio of 1.81 (95% confidence interval, 1.06–3.07).Conclusion: Published evidence is not sufficient to support the routine use of new protein markers in screening for ACS in the emergency department setting.