Open Access Correspondence

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

Lauren B Gerson1, George Triadafilopoulos1, Peyman Sahbaie2, Winston Young3, Sheldon Sloan4, Malcolm Robinson5, Philip B Miner5 and Jerry D Gardner6*

Author Affiliations

1 Stanford University School of Medicine, Stanford, CA, USA

2 Veterans Affairs Palo Alto Health Care System, Palo Alto, CA, USA

3 Blossomtech, Inc., Apex, NC, USA

4 Janssen Pharmaceutica Inc., Titusville, NJ, USA

5 Oklahoma Foundation for Digestive Research, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA

6 Science for Organizations, Inc., Mill Valley, CA, USA

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BMC Gastroenterology 2008, 8:15  doi:10.1186/1471-230X-8-15

Published: 23 May 2008



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.


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


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.


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.


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.