Impedance baseline and reflux perception in responder and non-responder non-erosive reflux disease patients

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) Omega vs 1667 (1361-1973) Omega, 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.