Background and aim: pH-impedance monitoring is used to diagnose symptomatic gastroesophageal reflux (GER) based on symptom association probability (SAP). Current criteria for calculation of SAP are optimised for heartburn in adults. Infants, however, demonstrate a different symptom profile. The aim of the present study was to optimise criteria for calculation of SAP in infants with GER disease.
Patients and methods: Ten infants referred for investigation of symptomatic reflux were enrolled. GER episodes were recorded using a pH-impedance probe, which remained in place for 48 hours. During the test, cough, crying, and regurgitation were marked. Impedance recordings were analysed for the occurrence of bolus reflux episodes. SAP for behaviors following reflux episodes was separately calculated for day 1 and day 2 using automated reporting software, which enabled the time window used for SAP calculations to be modified from 15 to 600 seconds. Day-to-day agreement of SAP was assessed by calculating the 95% limits of agreement (mean difference ± 1.96 standard deviations of differences) and their confidence intervals.
Results: The number of bolus GER episodes and symptom episodes reported did not differ from day to day. The best agreement in SAP between the 2 days was found using time intervals of 2 minutes for cough, 5 minutes for crying, and 15 seconds and/or 2 to 5 minutes for regurgitation.
Conclusions: We conclude that the standard 2-minute time interval is appropriate for the investigation of cough and regurgitation symptoms. The day-to-day agreement of SAP for crying was poor using standard criteria, and our results suggest increasing the reflux-symptom association time interval to 5 minutes.