• oesophageal pH
• Barrett's oesophagus
• pH monitoring

We wish to comment on an interesting paper published previously in Gut which we inadvertently overlooked at the time. Fass et al (Gut 2001;48:310–13) reported that there was a positive correlation between percentage time that oesophageal pH was less than 4 in 24 hours and the length of the columnar lined segment in 15 patients with long segment Barrett's oesophagus. Some years ago, we published data concerning 24 hour ambulatory oesophageal pH monitoring in untreated patients with Barrett's oesophagus and compared the results with those obtained in patients with reflux oesophagitis but no Barrett's oesophagus.¹ pH monitoring was performed within one week of endoscopy. We found overlap in the 24 hour pH results between Barrett's patients and patients with reflux oesophagitis. However, among Barrett's patients, those with moderate to severe reflux oesophagitis above Barrett's segment had more acid reflux than those with mild reflux oesophagitis or none. At the time we did not correlate pH monitoring results with the length of the Barrett's segment but have now reviewed our pH data and have been able to correlate these results with the length of the columnar lined …