Reflux monitoring: on or off therapy?

The role of esophageal pH (or impedance) monitoring in diagnosing gastroesophageal reflux disease (GERD) has evolved over the years. In the era of empiric therapy with potent acid-suppressive agents such as proton pump inhibitors (PPIs), esophageal reflux monitoring is often reserved for patients with PPI-refractory symptoms (1, 2). Given the complexity of patient presentations, technological advancement, and emerging data in the field of GERD, two essential questions need to be addressed: (i) What are the indications for esophageal pH testing in patients suspected to have GERD? (ii) If patients do not respond to aggressive acid suppression, what is the likelihood that they still have reflux; and should the testing be performed at baseline (i.e., off therapy), or is it more important to know whether there is continued reflux despite therapy (i.e., on therapy)?