EDITORIAL Ambulatory Monitoring for Gastroesophageal Reflux Disease: Where Do We Stand? he role of ambulatory monitoring in diagnosing gastroesophageal reflux disease (GERD) has evolved over the years. Impedance monitoring has provided the opportunity to detect esophageal exposure to both acid and non-acid reflux events and has increased sensitivity of reflux monitoring.1 In the era of empiric therapy with potent acid suppressive agents such as proton pump inhibitors (PPIs), esophageal reflux testing is often reserved for patients with PPI refractory symptoms.2,3 In cases of refractory symptoms, the question remains: what is the role of continued reflux events (acid or non-acid) in patients’ unresolved symptoms? To this end, controversy remains whether such testing should be performed on or off PPI therapy. In this issue of the journal, Patel et al4 report on predictors of reflux treatment outcome in a large cohort of patients with GERD. They studied 187 subjects with persistent reflux symptoms despite antisecretory therapy who had undergone pH-impedance testing either on or off therapy before subsequent medical or surgical intervention. Tests were performed in equal proportions of patients on or off therapy, and validated questionnaires were used to assess symptom improvement over time. After nearly 40 months of follow-up, they reported symptom improvement (>50% from baseline) in more than half of their subjects. Importantly, multivariate analysis showed that abnormal esophageal acid exposure at baseline off PPI therapy consistently predicted symptomatic outcome after therapy. Other predictors included impedance nonacid–detected symptom association probability (SAP) and older age. Abnormal reflux exposure time, acidrelated symptom index (SI) or acid-related SAP, and number of reflux events by impedance testing were not significant predictors of outcome. Patel et al4 are to be congratulated for addressing this important and often controversial issue. However, their findings must be considered within the context of the debate surrounding reflux monitoring.

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Should One Use Impedance Testing or Can pH Testing Alone Be Sufficient? There is little doubt that pH-impedance testing provides a more sensitive means of comprehensively identifying reflux events in a given patient.1 However, to date, studies have failed to demonstrate that it provides any significant additional clinical benefit. First, caution must be exercised when incorporating the added objective Clinical Gastroenterology and Hepatology 2015;13:892–894

data from non-acidic or weakly acidic reflux events into treatment decision-making because altered patient behavior related to catheter testing can decrease the sensitivity of reflux monitoring. Specifically, patients do not enjoy having a catheter that passes through their nose and down the back of their throat. They frequently comment that it is difficult to “have a normal day” as instructed. Wireless pH testing is generally better tolerated and provides longer measurement duration, which can better account for known day-to-day test variability in pH-impedance events. Second, there has been a discrepancy in findings since initial optimistic reports of improved patient outcome that were based on impedance data.5 In fact, recent studies including Patel et al4 have not shown that knowledge regarding continued non-acid or weakly acid reflux events alter patient outcome. For example, Francis et al6 evaluated outcome of surgical fundoplication in patients with chronic cough who had undergone pH testing off PPI therapy and impedance-pH testing on PPI therapy. They reported that impedance testing on therapy did not predict surgical outcome. Importantly, they showed that predictors of favorable symptomatic outcome after surgery included baseline presence of typical symptoms of heartburn and/ or regurgitation, % time pH