Time esophageal pH < 4 overestimates the prevalence of pathologic esophageal reflux in subjects with gastroesophageal reflux disease treated with proton pump inhibitors

Abstract

Background: A Stanford University study reported that in asymptomatic GERD patients who were being treated with a proton pump inhibitor (PPI), 50% had pathologic esophageal acid exposure.

Aim: We considered the possibility that the high prevalence of pathologic esophageal reflux might simply have resulted from calculating acidity as time pH < 4.

Methods: We calculated integrated acidity and time pH < 4 from the 49 recordings of 24-hour gastric and esophageal pH from the Stanford study as well as from another study of 57 GERD subjects, 26 of whom were treated for 8 days with 20 mg omeprazole or 20 mg rabeprazole in a 2-way crossover fashion.

Results: The prevalence of pathologic 24-hour esophageal reflux in both studies was significantly higher when measured as time pH < 4 than when measured as integrated acidity. This difference was entirely attributable to a difference between the two measures during the nocturnal period. Nocturnal gastric acid breakthrough was not a useful predictor of pathologic nocturnal esophageal reflux.

Conclusion: In GERD subjects treated with a PPI, measuring time esophageal pH < 4 will significantly overestimate the prevalence of pathologic esophageal acid exposure over 24 hours and during the nocturnal period.

Figure 1

Prevalence of pathologic 24-hour esophageal acidity assessed with integrated acidity and time pH < 4 in the index study (n = 46). The left panel gives prevalence with the 95% confidence interval. The right panel gives values for time pH < 4 from records with normal integrated acidity.

Figure 2

Prevalence of pathologic postprandial esophageal acidity assessed with integrated acidity and time pH < 4 in the index study (n = 46). The left panel gives prevalence with the 95% confidence interval. The right panel gives values for time pH < 4 from records with normal integrated acidity.

Figure 3

Prevalence of pathologic nocturnal esophageal acidity assessed with integrated acidity and time pH < 4 in the index study (n = 46). The left panel gives prevalence with the 95% confidence interval. The right panel gives values for time pH < 4 from records with normal integrated acidity.

Figure 4

Prevalence of pathologic esophageal acidity assessed with integrated acidity and time pH < 4 in the 3rd study (n = 52 records). Data are from 24-hour esophageal recordings on the 8^th day of treatment with 20 mg omeprazole or 20 mg rabeprazole. Vertical bars give the 95% confidence interval.