Risk assessment scores and clinical prediction algorithms using clinical history, physical examination, ECG, and car- diac troponins have been developed to help identify patients with ACS at increased risk of adverse outcome(s). Common risk assessment tools include the TIMI (Thrombolysis In Myocardial Infarction) risk score,42 the PURSUIT (Platelet Glycoprotein IIb/IIIa in Unstable Angina: Receptor Suppression Using Integrilin Therapy) risk score,43 the GRACE (Global Registry of Acute Coronary Events) risk and the NCDR-ACTION (National Cardiovascular Data Registry-Acute Coronary Treatment and Intervention Outcomes Network) registry (https://www.ncdr.com/webncdr/ action/). These assessment tools have been applied with vari- able efficacy to predict outcomes in patients presenting to the emergency department (ED) with undifferentiated chest pain ( pain encompasses not only pain, but also symptoms such as discomfort, pressure, and squeezing).45 48 The Sanchis score,49 Heart (History, ECG, Age, Risk Factors, and Troponin) score,51 and Hess prediction were developed specifically for patients in the ED with chest pain. Although no definitive study has demonstrated the superiority of risk assessment scores or clinical prediction rules over clinician judgment, determination of the level of risk on initial evaluation is imperative to guide patient man- agement, including the need for additional diagnostic testing and treatment. See Section 3.2.2 for a discussion of risk strati- fication variables. See Online Data Supplement 1 for additional information on clinical assessment and initial evaluation. 3.1.1. ED or Outpatient Facility Presentation: Recommendations Class I 1. Patients with suspected ACS and high-risk features such as continuing chest pain, severe dyspnea, syn- cope/presyncope, or palpitations should be referred immediately to the ED and transported by emer- gency medical services when available. (Level of Evidence: C) Class IIb 1. 