Final answer:
The tilt-table test is the most helpful test in identifying the cause of this patient's symptoms.
Step-by-step explanation:
The test that is most helpful in identifying the cause of this patient's symptoms is Tilt-table test.
The symptoms described by the patient are consistent with orthostatic hypotension, which is a decrease in blood pressure when changing from a supine to a standing position. The drop in systolic blood pressure of 24 mm Hg is suggestive of this condition. The tilt-table test involves strapping the patient to a table that can be tilted to different angles, allowing the healthcare provider to monitor the individual's blood pressure and heart rate in different positions. This test can help determine if the patient's symptoms are due to orthostatic hypotension.