In the emergency department, how useful is knowing the patient's risk factors when predicting the likelihood of an acute coronary syndrome?
The presence or absence of cardiac risk factors does not help to determine whether a patient with symptoms will have acute coronary syndrome (ACS). In patients older than 65 years, even the presence of 4 or 5 risk factors does not predict the likelihood of ACS (likelihood ratio = 1.2). Although their risk of having a cardiac event was higher over time because of their risk factors, at the time of symptom presentation these patients were no more likely to have an ACS than people with fewer or no risk factors with similar symptoms. In patients younger than 40 years, the presence of 4 or more risk factors is moderately predictive of ACS (likelihood ratio = 7.4). (LOE = 1b)
Han JH, Lindsell CJ, Storrow AB, et al. The role of cardiac risk factor burden in diagnosing acute coronary syndromes in the emergency department setting. Ann Emerg Med 2007;49:145-52. [PMID:17145112]
To answer this question, the researchers used an Internet tracking system that collected data on 10,806 eligible patients presenting to emergency departments with possible acute coronary syndromes. Data were entered using a convenience sample of patients prospectively enrolled in 8 emergency departments in the United States. Emergency department-recorded positive risk factors -- diabetes, hypercholesterolemia, hypertension, smoking, and family history -- were each given equal weight. Thirty-day follow-up was performed to find out the diagnosis and was completed in more than 95% of patients. ACS occurred in 8.1% of the patients in the study. For patients younger than 40 years, the area under the receiver operating characteristic curve was 0.763, indicating fair diagnostic performance. The presence of risk factors had little diagnostic utility in patients older than 40 years and the estimated likelihood of ACS in patients older than 65 years was no better than that occurring by chance. For example, the positive likelihood ratio for 4 or 5 risk factors in patients aged 40 years to 65 years was only 2.13; in patients older than 65 years it was only 1.09. Negative likelihood ratios for these age groups was 0.92 and 1.00.
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