To investigate the clinical significance of esophageal mean nocturnal baseline impedance (MNBI) in patients with extra-esophageal symptoms of gastroesophageal reflux disease (GERD).

We performed a retrospective study of 210 patients with heartburn, reflux, cough, and hoarseness as their main symptoms who underwent 24-hour multichannel intraluminal impedance and pH monitoring in Beijing ChaoYang hospital from January 2018 to December 2019.According to diagnostic criteria and their main clinical manifestations, patients were divided into four groups, the extra-esophageal symptoms group, the typical symptoms group, the mixed symptom group with both typical and extra-esophageal symptoms, and the control group.We analyzed and compared distal and proximal esophageal MNBI value and other reflux parameters among the four groups.

The proximal esophageal MNBI value and mean pH at distal esophagus in GERD extra-esophageal symptoms group were lower than those in the typical symptom group (P<0.05). Correlation analysis showed that the proximal and distal esophageal MNBI value were negatively correlated with DeMeester score, acid exposure time and acid reflux times (P<0.05). According to ROC analysis, for GERD patients with extra-esophageal symptoms, area under curve of the proximal esophagus MNBI value was significantly higher than the area under curve of the distal esophageal MNBI value (P<0.05), the cut-off value for diagnosis was 2484.38 ohms. The sensitivity and accuracy of the proximal esophageal MNBI value in diagnosis GERD patients with extra-esophageal symptoms reached 92.3% and 84%, which were higher than those of the distal esophageal MNBI value.

Both the proximal and distal esophagus MNBI values negatively correlate with acid exposure. Proximal esophagus MNBI value can improve the detection rate of multi-channel pH-impedance monitoring for patients with extra-esophageal symptoms of GERD, which has important clinical diagnostic value.