Measurement of Esophageal Nocturnal Baseline Impedance: A Simplified Method

Abstract

Background/Aims Mean nocturnal baseline impedance (MNBI) during multichannel intraluminal impedance pH-monitoring (MII-pH) reflects the status of esophageal mucosal integrity. MNBI is suggested as an adjunctive method to distinguish patients with true gastroesophageal reflux disease (GERD) from functional heartburn (FH) and might predict outcomes for anti-reflux treatment. However, current methodology for calculation of MNBI is time-consuming and subject to operator-dependent selection bias. We aim to simplify and provide a more objective method to calculate MNBI. Methods We retrospectively analyzed 100 MII-pH tracings from 20 patients with erosive reflux disease, 20 with non-erosive reflux disease (NERD), 20 with reflux hypersensitivity, 20 with functional heartburn (FH), and 20 healthy asymptomatic volunteers. We compared the current "conventional" MNBI analysis with our "simple" MNBI analysis measured by selecting the whole supine period using the impedance average calculation function in the MII-pH software. Results Absolute values were very similar and there was a strong correlation between conventional and simple MNBI values in the most distal channel in all groups (r ≥ 0.8, P < 0.001) including patients with increased supine acid reflux. Distal esophageal simple MNBI negatively correlated with acid exposure time (r =-0.695, P < 0.001). Patients with erosive reflux disease and NERD had lower simple MNBI values in the most distal channel compared to other groups (P < 0.001). With a cutoff value of 1785 ohms, simple MNBI can discriminate patients with GERD from those with reflux hypersensitivity and FH (sensitivity 80.0% and specificity 89.7%). Conclusion Simple MNBI analysis provides very similar values and has an excellent correlation with conventional MNBI analysis.

Conventional and simple methods of measuring esophageal nocturnal baseline impedance show excellent agreement

“…This method has been introduced as a faster and less selective way of obtaining MNBI, and is representative of the whole nocturnal recumbent period. In this study, MNBI values obtained by conventional and simple methods strongly correlated 5 . To our knowledge, no other studies have yet validated the simple MNBI measurement method.…”

“…The Spearman's correlation test was used in one study 5 to compare the two MNBI measurement methods. This test assesses the relationship between two variables, not the difference, and so lacks the ability to detect bias in method comparison studies, particularly proportional and fixed bias 9,10 …”

The Value of Reflux Monitoring: The Old and the New for the Diagnosis and Assessment of GERD

“…There are 2 methods of calculation; baseline impedance can be averaged from 3 10-minute periods during the 1 to 3 AM nocturnal period, 38 or from the entire nocturnal recumbent period. 43 Baseline impedance is higher in healthy controls, healed esophagitis, PPI-responsive NERD, and functional esophageal disorders compared to erosive esophagitis, and PPI-refractory NERD. 38,40,[44][45][46][47] Low MNBI independently predicts response to antireflux therapy, 48 especially when AET is borderline or inconclusive.…”

Editorial: inconclusive diagnosis of GERD: are new parameters in impedance‐pHmetry ready for clinical use? Authors' reply

“…However, much of the time required for the calculation of the PSPW index is due to manual assessment of reflux episodes, in turn often unreliably detected by automated analysis, 8 a simplified method for MNBI calculations has recently been proposed. 9 It is conceivable that artificial intelligence will be helpful in the calculation of impedance variables in the near future. 10 In summary, the diagnosis of GERD is often challenging, and also crucial, in order to better direct patients to appropriate treatment.…”