Risk Stratification in Non-ST-segment Elevation Acute Coronary Syndromes: Troponin Alone Is not Enough
Article Outline
Non-ST-segment elevation acute coronary syndromes include a heterogeneous group of patients in terms of presentation and outcomes. Thus, risk stratification of these individuals is critical and relies upon clinical, electrocardiographic, and biochemical assessment. Although scores combining these factors correlate to the risk of death and myocardial infarction,1, 2, 3, 4, 5 they are often not used.
Because troponins are highly sensitive and specific markers of myocardial injury, and as they are correlated to the benefit of antiplatelet therapies and interventions, there is a temptation to reduce risk stratification in acute coronary syndromes to troponins alone. Indeed, in routine practice, many physicians simply equate “troponin positive” to “high risk.” Yet, this is an oversimplistic approach to risk stratification, which may explain the disconnect between perceived and actual risk.6, 7
In the Global Registry of Acute Coronary Events (GRACE) registry, we examined the distribution of GRACE risk score, a validated tool to predict in-hospital and postdischarge mortality1, 2, 4, 5 in 27,406 patients with non-ST-segment elevation acute coronary syndromes. The prevalence of troponin positivity in each category of risk score was examined in relation to hospital mortality. As shown in the Figure, the GRACE risk score had a direct relation to hospital mortality. However, although there was an increased prevalence of troponin positivity with increasing GRACE risk score, troponins fell short of robust risk stratification in 2 ways: a large proportion of troponin-positive patients were in the low-to-medium risk group; conversely, some very-high-risk patients had negative troponins. Dividing patients into deciles of risk, hospital death rates for troponin-positive patients ranged from 0% in the lowest decile to 15.0% in the highest risk decile. Therefore, many troponin-positive patients were at low risk for mortality. Conversely, there was a spectrum of risk among troponin-negative patients, with death rates ranging from 0.1% in the lowest to 12.7% in the highest risk decile. Corresponding 6-month mortality rates ranged from 0.9% to 19.8% in troponin-positive patients and from 0.2% to 13.3% for troponin-negative patients. Therefore, troponin positivity alone is not a reliable predictor of in-hospital or 6-month mortality.
Figure.
The bar chart describes the distribution of (left axis) troponin positive (white bars) and troponin negative (black bars) patients according to category of GRACE risk score (ranging from <51 to >226) among 27,406 patients with non-ST-segment elevation acute coronary syndromes in the GRACE registry. The black curve (right axis) depicts the observed hospital mortality rates.
Although troponin provides important prognostic information, it does not accurately measure risk, particularly when used in a binary fashion. Risk stratification tools (such as the GRACE, Thrombolysis In Myocardial Infarction, or other scores) that integrate clinical, electrocardiographic, and biochemical information provide more precise estimation of risk that is useful for triaging patients for pharmacologic and interventional therapies. Binary approaches to risk stratification, although simple and seductive, can be deceptive.
References
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Funding: The GRACE registry is funded by a research grant from sanofi-aventis.
Conflict of interest: Dr. Steg reports having received honoraria as speaker or consultant from Astellas, AstraZeneca, Bayer, Boehringer-Ingelheim, BMS, Endotis, GSK, Medtronic, MSD, Nycomed, sanofi-aventis, Servier, The Medicines Company. In addition, his institution has received a research grant from sanofi-aventis in the past 7 years. Dr. FitzGerald has no disclosures. Dr. Fox reports having received honoraria as speaker or consultant and research grants from Sanofi-aventis, GSK and Merck, Sharpe and Dohme.
Authorship: All authors had access to the data and a role in writing the manuscript.
PII: S0002-9343(08)00972-8
doi:10.1016/j.amjmed.2008.07.029
© 2009 Elsevier Inc. All rights reserved.
