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

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.