Background: It was recently shown that GERD patients have lower impedance baseline (IB) values than healthy controls and, that the esophageal acid exposure time (AET) correlates with IB levels.
Goals: To explore the sensitivity of IB measurements in NERD patients, responders and non-responders to PPIs, when compared with pH-impedance (MII-pH) variables, and to evaluate whether this variable could represent a marker of GERD symptoms. Reproducibility and inter-observer agreement of IB measurement were also assessed. Study. MII-pH tracings from 44 NERD responders and 22 non-responders were analysed. Ten healthy volunteers underwent the same protocol. IB values were measured at the distal and proximal esophagus. IB was also analysed in a subgroup of patients and in controls with two methods and by two blinded operators.
Results: Mean IB values at the distal esophagus were significantly lower in NERD patients than in controls. IB values did not differ between responders and non-responders. Of the 8 responders with negative AET and symptom association probability (SAP), 3 (37.5%) showed IB values lower than controls. IB values in responders with positive and negative SAP were similar (1832 (1596-2068) Ω vs 1667 (1361-1973) Ω, p: n.s.). No differences were found between the IB values measured with the two methods and the inter-observer agreement was good.
Conclusions: IB is a promising and easy to calculate MII-pH variable and appears to increase the sensitivity of MII-pH monitoring. IB values cannot predict PPI response and are not associated with reflux perception in NERD patients.