Will esophageal impedance replace pH monitoring?

Esophageal impedance, a technique based on the fact that the passage of a bolus changes the impedance between esophageal segments, is being used more and more. Multiple esophageal impedance combined with pH monitoring is advocated to become the preferred technique to measure acid and nonacid gastroesophageal reflux. Compared with pH monitoring, impedance has the advantage of being independent of pH and, as a consequence, is better adapted to measure reflux (especially in the postprandial period when reflux is buffered) and detect symptoms associated with nonacid- or weakly acid-reflux episodes. Conversely, the analysis of an impedance tracing requires more time and knowledge than a pH tracing and is possibly subjected to higher interobserver variability. Day-to-day reproducibility and interobserver variability are considerable. Episodes detected only by pH monitoring or impedance are numerous in pediatrics; therefore, pH monitoring and impedance should be associated in analyses of multiple esophageal impedance combined with pH monitoring. Up to now, there has been a striking absence of literature showing attempts to link data from diagnostic procedures to clinical outcome in symptomatic patients. Furthermore, data suggesting that impedance does offer a clear-cut benefit in pediatric clinical routine are missing. High cost of the material and the investment in time necessary for interpretation of the recording remain a handicap. However, because pH monitoring is part of impedance technology, it is likely that the latter will soon replace pH monitoring despite the current need of scientific evidence demonstrating a relation between symptoms, esophageal damage or response to reflux treatment, and results of multiple esophageal impedance combined with pH monitoring.