Impedance-pH monitoring on medications does not reliably confirm the presence of gastroesophageal reflux disease in patients referred for antireflux surgery

Surg Endosc. 2018 Feb;32(2):889-894. doi: 10.1007/s00464-017-5759-7. Epub 2017 Aug 4.


Introduction: The gold standard for the objective diagnosis of gastroesophageal reflux disease (GERD) is ambulatory-pH monitoring off medications. Increasingly, impedance-pH (MII-pH) monitoring on medications is being used to evaluate refractory symptoms. The aim of this study was to determine whether an MII-pH test on medications can reliably detect the presence of GERD.

Methods: Patients referred for persistent reflux symptoms despite pH confirmed adequate acid suppression (DeMeester score ≤14.7) were reviewed retrospectively. All patients who originally had MII-pH testing on medications were re-evaluated with an off medication Bravo-pH study. Acid exposure results (defined by off medication Bravo) were compared to the original on medication MII-pH.

Results: There were 49 patients who met study criteria (median age 51). Patients had normal acid exposure during their MII-pH test on medications (average DMS 4.35). Impedance was abnormal (normal ≤47) in 25 of the 49 patients (51%). On subsequent Bravo-pH off medications, 37 patients (75.7%) showed increased esophageal acid exposure (average DMS 36.4). Bravo-pH testing was abnormal in 84% of patients with abnormal MII testing and in 67% with normal MII testing. The sensitivity and specificity of an abnormal MII-pH on medications for increased esophageal acid exposure off medications was 56.8 and 66.7%, respectively. The positive predictive value of confirming GERD from an abnormal MII-pH on medications is 84%, while the negative predictive value is 33.3%. A receiver operating characteristic (ROC) curve was generated and the area under the curve was 0.71, indicating that MII-pH on medications is a fair test (0.7-0.8) in diagnosing pathologic GERD.

Conclusion: Compared to the gold standard, MII-pH on medications does not reliably confirm the presence of GERD. Excellent outcomes with antireflux surgery are dependent on the presence of GERD; thus, patients should not be offered antireflux surgery until GERD is confirmed with pH testing off medications.

Keywords: Antireflux surgery; Bravo-pH testing; Gastroesophageal reflux disease (GERD); Impedance-pH testing; Proton pump inhibitor (PPI).

Publication types

  • Comparative Study

MeSH terms

  • Adult
  • Aged
  • Antacids / therapeutic use
  • Electric Impedance
  • Esophageal pH Monitoring / methods*
  • Female
  • Gastroesophageal Reflux / diagnosis*
  • Gastroesophageal Reflux / drug therapy
  • Gastroesophageal Reflux / surgery
  • Humans
  • Male
  • Middle Aged
  • ROC Curve
  • Retrospective Studies
  • Sensitivity and Specificity


  • Antacids