Which differential diagnosis is associated with shortness of breath and has a key differentiating test of ECG and troponin?

• A. Acute coronary syndrome — ECG and troponin
• B. Pneumonia — chest radiograph
• C. COPD — spirometry
• D. Asthma — spirometry

Answer: (A)

Shortness of breath can be caused by heart problems, and when the concern is ACS, ECG and troponin are the tests that most clearly distinguish it. Acute coronary syndrome is diagnosed by looking for ischemic changes on the ECG—such as ST-segment elevation or depression, T-wave changes, or new conduction abnormalities—and by elevated troponin levels, which reflect myocardial injury. Troponin is a highly specific marker for heart muscle damage and rises within a few hours of onset, providing crucial confirmation alongside the ECG.

Pneumonia, in contrast, is primarily identified with chest imaging showing infiltrates and clinical signs like fever and productive cough. COPD and asthma are evaluated mainly with spirometry, showing obstructive patterns and, for asthma, reversible airway limitation after bronchodilators. While troponin can be checked if there’s concern for a heart attack in a patient with SOB, these conditions are not defined by ECG and troponin testing.

So, the condition associated with shortness of breath for which ECG and troponin serve as the key differentiating tests is acute coronary syndrome.