Accuracy of the traditional pH criterion for gastro-oesophageal reflux

Objective: To assess the accuracy of the traditional pH criterion for gastro-oesophageal reflux (i.e. fall of intra-oesophageal pH below 4) in a group of healthy volunteers. Design: Intra-oesophageal pH and motility of the pharynx, oesophageal body, lower oesophageal sphincter (Dentsleeve) and stomach were recorded in 19 healthy volunteers for a mean of 138 min (range 90-200 min) after a 700 Kcal mixed nutrient meal. Methods: The traditional pH criterion for gastro-oesophageal reflux was compared with a non-traditional one which was used as a standard. According to this criterion a reflux episode was an abrupt pH fall of ≥1 unit during a complete relaxation of the lower oesophageal sphincter and/or during a common cavity phenomenon. Results: The traditional criterion significantly (P <0.01) underscored reflux episodes by a mean of -1.2 episodes per volunteer with a 95% confidence interval (CI) from -1.6 to -0.8. The degree of inaccuracy varied little among the volunteers and a high correlation was found between number of reflux episodes per volunteer according to the two criteria (r = 0.95, P <0.001). Conclusions: The traditional criterion for gastro-oesophageal reflux underestimates the number of reflux episodes. However, the number of traditional reflux events seems to be a reliable index of the real number of reflux episodes, at least in our experimental conditions.