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Updated: Aug 10, 2025
Construction of a Wireless-Enabled Endoscopically Implantable Sensor for pH Monitoring with Zero-Bias Schottky Diode-based Receiver
Published on: August 27, 2021
On-therapy impedance-pH monitoring can efficiently characterize PPI-refractory GERD and support treatment escalation
Marzio Frazzoni1, Leonardo Frazzoni2, Mentore Ribolsi3
1Digestive Pathophysiology Unit and Digestive Endoscopy Unit, Azienda Ospedaliero Universitaria di Modena, Ospedale Civile di Baggiovara, Modena, Italy.
Background:
On-therapy impedance-pH monitoring is recommended in patients with documented GERD and PPI-refractory heartburn in order to establish whether the unremitting symptom is reflux-related or not.
Aims:
To define on-PPI cut-offs of impedance-pH metrics allowing proper interpretation of on-therapy impedance-pH monitoring.
Methods:
Blinded expert review of impedance-pH tracings performed during double-dosage PPI, prospectively collected from 150 GERD patients with PPI-refractory heartburn and 45 GERD patients with PPI-responsive heartburn but persisting extra-esophageal symptoms. Acid exposure time (AET), number of total refluxes (TRs), post-reflux swallow-induced peristaltic wave (PSPW) index, and mean nocturnal baseline impedance (MNBI) were assessed. On-PPI cut-offs were defined and evaluated with ROC analysis and the area under curve (AUC).
Results:
All the four impedance-pH metrics significantly differed between PPI-refractory and PPI-responsive heartburn cases. At ROC analysis, AUC was 0.73 for AET, 0.75 for TRs, 0.81 for PSPW index, and 0.71 for MNBI; best cut-offs were ≥1.7% for AET, ≥45 for TRs, ≤36% for PSPW index, and ≤ 1847 Ω for MNBI; AUC of such cut-offs was 0.66, 0.71, 0.73, and 0.68, respectively. Analysis of PSPW index and MNBI added to assessment of AET and TRs significantly increased the yield of on-therapy impedance-pH monitoring in the PPI-refractory cohort (97% vs. 83%, p < 0.0001). Notably, suboptimal acid suppression as shown by AET ≥1.7% was detected in 43% of 150 PPI-refractory cases.
Conclusions:
We have defined on-PPI cut-offs of impedance-pH metrics by which comprehensive assessment of impedance-pH tracings, including analysis of PSPW index and MNBI can efficiently characterize PPI-refractory GERD and support treatment escalation.
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