S0437 Impact of Incorporating Mean Nocturnal Basal Impedance as a Supplemental Metric to Acid Exposure Time in Patients With Esophageal Symptoms

Abstract

INTRODUCTION: While acid exposure time (AET) predicts response to anti-reflux treatment and is the most validated parameter of pH monitoring, it is limited by daily variations and does not directly evaluate tissue damage. However, Distal mean nocturnal basal impedance (dMNBI) does measure gastroesophageal reflux (GER) related damage (increased mucosal permeability). dMNBI is validated to assess response to anti-reflux treatment and has become a valuable supplemental metric to AET. We report the impact of combining AET with dMNBI for classifications of gastroesophageal reflux disorder (GERD) including pathologic GER, esophageal hypersensitivity (EH), and functional symptoms (FS). METHODS: Patients who underwent pH-impedance monitoring off of proton pump inhibitor (PPI) therapy for refractory GERD at our center from Oct 2013 to March 2020 were included. Those with achalasia, esophagogastric junction outflow obstruction, scleroderma, and those evaluated for cough were excluded. dMNBI was calculated as the average impedance of three uninterrupted 10-minute intervals collected at night 3 cm proximal to the GE junction. dMNBI < 2.29 or AET >6% were considered abnormal. EH was defined as AET< 6% and/or dMNBI< 2.29kOhm with a symptom association probability (SAP) > 95%. FS was defined as AET< 6% and/or dMNBI< 2.29 kOhm and SAP < 95%. RESULTS: A total of 267 patients underwent pH-impedance monitoring off of PPI therapy. 206 patients were included in the analysis. 5 patients completed less than 12 hours of the study and 46 met exclusion criteria. The mean age was 50 (±15) years, 150 (73%) were females, 162 (79%) were Caucasian, 93 (46%) were current or former smokers, and mean BMI was 31 (±7). The AET was abnormal in 53 (26%), intermediate in 19 (9%), and normal in the remainder. With AET alone, 26% were classified as pathological GER, 23% were EH, 32% were FS, and 19% were undetermined (Figure 1). Combined AET and dMNBI based classification resulted in pathological GER in 46%, EH in 13%, FH 23%, and undetermined in 17% (Figure 2). This difference in classification was statistically significant (P < 0.0001). CONCLUSION: Using dMNBI in conjunction with AET identifies a significant proportion of patients with GERD and decreases patients classified with FS. This has an important clinical impact as GERD patients receive different treatment than patients with functional symptoms. Enhancing AET with dMNBI facilitates more accurate diagnoses and aids in the future management of patients with esophageal conditions.Figure 1.: Outcome classification by acid exposure time (AET) alone.Figure 2.: Outcome classification by combined acid exposure time (AET) and distal mean nocturnal basal impedance (dMNBI).