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PATIENT CASE

A 35-year-old man arrives by ambulance to the emergency department (ED) with chief complaints of chest pain, shortness of breath, nausea, and dizziness. Physician interviews reveal no relevant risk factors for cardiovascular disease and no family history of cardiovascular events. Because his electrocardiogram (ECG) does not show any alterations, and the chest x-ray is normal, he is promptly discharged with possible diagnoses of influenza or stress. A few days later, he returns to the ED for severe chest pain accompanied again by shortness of breath and dizziness. Both ECG and chest x-ray do not show relevant alterations, so he is again discharged. Less than 30 hours later, he is found on his kitchen floor, unresponsive. First responders declare him dead at 3:30 that morning. The following day, his autopsy reveals the cause of death: aortic dissection.

Biomarkers have risen to popularity for their ability to promote timely diagnoses, reveal prognostic information, monitor disease progression, and predict therapeutic response. In the context of emergency medicine, biomarkers can serve as rule-in or rule-out diagnostic tools to supplement the emergency physician’s knowledge and judgment. In the Patient Case above, laboratory tests may have served both secondary and tertiary prevention roles in the optimal course of treatment. In the context of the continuous management of a chronic disease, such as heart failure (HF), biomarkers can help evaluate whether therapies are effective, guide management, and predict adverse outcomes.1,2

DIFFERENTIAL DIAGNOSIS

In the ED, the most common and concerning symptoms are nontraumatic chest pain and shortness of breath, especially among older populations; they represent, respectively, 9% to 10% of ED complaints, followed by abdominal pain and general weakness. This equates to more than 1.5 million visits out of a total of more than 5.0 million visits a year in the United States alone, and this figure has steadily grown over the past decade. Often, patients experience concomitant chest pain and shortness of breath, but dizziness, nausea, and diaphoresis can commonly present as well.1

Cases with these symptoms share a wide variety of etiologies; the most concerning, ie, those that must be most promptly included or excluded, can either have cardiac or respiratory etiologies. Acute myocardial infarction (AMI), acute heart failure (AHF), aortic dissection, and pulmonary embolism (PE) are the most common diagnoses, but pneumothorax, asthma, or a panic attack can present with these symptoms. For this reason, accurate and specific diagnostic techniques are crucial for timely treatment. The patient’s history, clinical evaluation with an accurate physical examination, biomarkers, and some diagnostic tools—such as ECG, x-ray, and other imaging techniques—are fundamental in identifying the disease.2 The efficacy depends on biomarker predictive accuracy; based on the etiology of biomarker release, the marker may have high sensitivity, specificity, positive predictive value, or negative predictive value (Figure 20-1).

Figure 20-1

The 4 main accuracy values associated with a quantitative ...

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