Reproducibility of Multichannel Intraluminal Electrical Impedance Monitoring of Gastroesophageal Reflux

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Abstract
Esophageal impedance measurement is a novel method for gastroesophageal reflux monitoring. Reproducibility is an important aspect of every biomedical test. The aim of this study was therefore to asses the reproducibility of gastroesophageal reflux monitoring using impedance measurements. Impedance and pH signals were recorded in 20 healthy volunteers during 90-min postprandial periods on two separate days. Hourly rates of gas, liquid, and mixed gas-liquid reflux episodes were measured in each recording period as well as percentage of time with pH < 4 and rate of acid reflux episodes. As a quantitative description of inter- and intraindividual variation for each variable, the mean percentage of covariation (100 × SD/mean: %COV) was calculated. As a second measure for reproducibility, Kendall's coefficients of concordance (W values) were calculated. For all variables, interindividual %COV was at least 50% higher than intraindividual %COV. Statistically significant concordances were found for gas reflux (W = 0.81, p = 0.04) and mixed reflux (W = 0.85, p = 0.03) while concordance for liquid reflux tended to be significant (W = 0.75, p = 0.08). This was comparable to the reproducibility of the number of acid reflux episodes and percentage of time with pH < 4 (W = 0.78, p = 0.05 and W = 0.88, p = 0.02, respectively). Postprandial gastroesophageal reflux data assessed with impedance monitoring are as reproducible as assessed with pH monitoring.