Esophageal chemical clearance and baseline impedance values in patients with chronic autoimmune atrophic gastritis and gastro-esophageal reflux disease

Background: The factors influencing new markers of gastro-esophageal reflux disease detected by impedance-pH monitoring - mean nocturnal baseline impedance (MNBI) and post-reflux swallow-induced peristaltic wave (PSPW) index - need to be evaluated. Aim: To compare endoscopy-negative heartburn with chronic autoimmune atrophic gastritis (CAAG). Materials and methods: 24 patients with CAAG, 25 with non-erosive reflux disease (NERD) and 25 with functional heartburn (FH) were included. In all patients the main impedance-pH monitoring parameters were calculated. Results: CAAG and NERD patients had a number of reflux events (non-acid ones being more common among the former group) which was higher than that found in FH (p. <. 0.001). MNBI decreased progressively in FH (>3000. Ohm), CAAG (>2000. Ohm) and NERD (<1000. Ohm) patients (p = 0.0046). The PSPW index was similar between CAAG and NERD patients but significantly lower in comparison to FH (p. <. 0.0001). Conclusion: Patients with CAAG have evidence of non-acid reflux based on the high number of reflux events and confirmed by low values of MNBI and PSPW index. MNBI is a strong marker of acid/non-acid reflux-induced mucosal damage, whereas the PSPW index can reliably discriminate patients with reflux from those with FH, independently of the acidity of refluxate.