Review Question - QID 214888

A 36-year-old man presents with a 4-month history of intermittent anxiety and headaches which typically last 20 minutes. The headaches are paroxysmal, 7/10 in intensity, and associated with diaphoresis and subjective palpitations. He is otherwise healthy and takes no medications. He denies a history of panic disorder or using tobacco, alcohol, or illicit drugs. His blood pressure was 118/72 mmHg at a business health fair last month. Intake vitals are temperature is 99.0°F (37.2°C), blood pressure is 125/75 mmHg, pulse is 65/min, and respirations are 16/min. During the interview, the patient suddenly becomes diaphoretic, reports palpitations, and develops a 7/10 headache. His vitals are repeated: temperature is 99.0°F (37.2°C), blood pressure is 185/115 mmHg, pulse is 135/min, and respirations are 19/min. Point of care blood glucose measurement is 188 mg/dL. Which of the following is the most appropriate initial diagnostic test for this patient?