Which test best assesses acid exposure over 24 hours?

• A. 24-hour ambulatory esophageal pH monitoring (often with impedance).
• B. Upper endoscopy with biopsies.
• C. Barium swallow.
• D. Esophageal manometry.

Answer: (A)

The test that directly measures how much time the esophagus spends exposed to acid over a full day is ambulatory esophageal pH monitoring. By placing a small sensor in the distal esophagus and having the patient go about normal activities for about 24 hours, we obtain a quantitative readout of acid exposure, such as the percentage of time with pH below 4 and related metrics like the DeMeester score. When this test is paired with impedance, it can also detect reflux episodes that don’t reach acidic levels, giving a fuller picture of reflux burden.

Upper endoscopy with biopsies looks for mucosal injury or structural problems but doesn’t quantify daily acid exposure. A barium swallow visualizes anatomy and some motility aspects, but it isn’t a reliable measure of acid exposure over time. Esophageal manometry maps pressure and peristalsis to assess motility and LES function, not acid exposure. So for measuring how much acid the esophagus encounters over 24 hours, ambulatory pH monitoring provides the direct, time-based data needed.