Reproducibility of ambulatory oesophageal pH monitoring.

To evaluate the reproducibility of ambulatory 24 hour intraoesophageal pH monitoring, 20 patients were randomly selected to undergo two consecutive investigations. Fifteen patients were classified as either abnormal, or normal on both test days. The amount of acid reflux, expressed as percentage of time with oesophageal pH below 4.0 during the two 24 hour periods, showed 77% concordance. The upright and recumbent periods of measurement showed different degrees of concordance: 83% and 62%, respectively. The reproducibility during time periods of different length was found to increase with increasing length of day time pH recording. A 16 hour period during evening and night had a reproducibility of only 58%, however. It is concluded that there is fairly good reproducibility when measuring gastro-oesophageal reflux over 24 hours, but that the reproducibility is poorer at night, during the postprandial period and when daytime monitoring is shorter than 10 hours.