Reproducibility of 24-hour combined multiple intraluminal impedance (MII) and pH measurements in infants and children. Evaluation of a diagnostic procedure for gastroesophageal reflux disease.

Gastroesophageal reflux disease (GERD) is a common disease in infants and children. Prolonged (24-hr) pH monitoring in the esophagus for determination of increased acid exposure has, together with endoscopy, been the only routinely implemented method for GERD diagnosis. The recently introduced multiple intraluminal impedance (MII) provides additional information about the number of both acid and nonacid episodes of retrograde bolus movement in the esophagus. The aim of this study was to investigate the day-to-day reproducibility and the interobserver variability of 24-hr combined MII (number of nonacid and acidic reflux episodes) and pH in the esophagus in infants and children. Upper endoscopy followed by 2 x 24-hr consecutive combined MII and pH monitoring was performed in 33 infants and children referred to a tertiary center for evaluation of GERD. The study was performed in a hospital setting without dietary restrictions. Bland-Altman difference versus mean plots and calculation of the limits of agreement (LOA) were used for assessment of the reproducibility of the total number of acidic and nonacidic reflux episodes. LOA for the number of acidic reflux episodes on day 2 were 0.2-5.3 times the value obtained on day 1. For the total number of nonacidic reflux episodes, LOA were 0.04-8.6; for the total number of reflux episodes, 0.3-3.3. An abnormal reflux index on one or both recording days was found in 7 of 30 patients. In conclusion, considerable day-to-day variability was found for nonacidic reflux episodes. Less variability was found for acidic reflux episodes. This variability must be taken into consideration for the use of MII in the clinical evaluation of infants and children with GERD.