Step 1: Answering clinical questions of diagnosis
You are seeing a 68-year-old man in clinic, because he is concerned about whether he has an aneurysm. His brother died of a ruptured aortic aneurysm, and he wonders whether he is at risk for the same problem. He denies abdominal or back pain. His past history is significant for coronary artery disease and hypertension. He continues to smoke 1 pack per day. On exam, he is thin and his heart, lung and extremity exam is unremarkable. On abdominal palpation, you find that he has an easily palpable aorta, and you measure the size to be about 2.5 cm. You wonder whether you should rely on your physical exam findings, or refer the patient for ultrasound to confirm that he doesn't have an aneurysm. His Medicare insurance will cover inpatient treatment only, and an ultrasound would not be covered.
By review of a textbook, you find that his major risk factors for an aneurysm are smoking, family history and coronary artery disease. He likely has a 10% chance of having an aneurysm.
Step 1: Define a clinical question
Continue to Step 2: Find evidence