Background Although proton pump inhibitors are the mainstay of gastroesophageal reflux disease treatment, up to 30% of patients have a poor symptomatic response. Ambulatory pH impedance monitoring is the gold standard to assess whether this is due to persistent acid reflux. We aimed to characterize clinical predictors of persistent esophageal acid reflux on proton pump inhibitors including gastric pH measured during endoscopy.

Methods We prospectively recruited patients with gastroesophageal reflux disease and/or Barrett esophagus on proton pump inhibitors. All patients completed a symptom questionnaire and underwent gastroscopy with gastric pH analysis, immediately followed by ambulatory 24-hour pH impedance. We used a modified cutoff of 1.3% for pathological esophageal acid exposure time. A multiple linear regression model was used to analyze the correlation between acid exposure time and predictive variables.

Results We recruited 122 patients, of whom 92 (75.4%) were included in the final analysis (44 male (47.8%), median age 53 years (interquartile range (IQR): 43–66)). Forty-four patients (47.8%) had persistent acid reflux with a median total acid exposure time of 2.2% (IQR: 1.2–5.0), compared with 0.1% (IQR: 0.0–0.2) in patients without persistent reflux (n = 48; p < .001). There was no difference in age, sex, body mass index, proton pump inhibitor regimen, diagnosis of hiatus hernia or Barrett esophagus, and severity of symptoms between patients with normal and abnormal acid exposure time. Median gastric pH was significantly lower in patients with persistent acid reflux (5.8 vs 6.6, p = .032) and it correlated with the total acid exposure time (p = .045; R2 = 12.0%). With a pH cutoff of 5.05, single-point endoscopic gastric pH analysis had an area under the receiver operating characteristic curve of 63.0% (95% confidence interval: 51.3–74.7) for prediction of persistent acid reflux.

Conclusions Symptoms and clinical characteristics are not useful to predict persistent acid reflux in patients on proton pump inhibitors. One-point gastric pH correlates with 24-hour esophageal acid exposure time and could guide clinicians to assess treatment response; however, its utility needs validation in larger studies.