Lower oesophageal sphincter identification for gastro-oesophageal reflux monitoring: The step-up method revisited with use of basal impedance.

Background: Oesophageal manometry is the gold standard for accurate positioning of multichannel intraluminal impedance pH (MII-pH) monitoring. The pH step-up method is not as accurate as oesophageal manometry and needs patients to be off proton pump inhibitor (PPI) therapy. Objective: This study aimed to evaluate the feasibility of the impedance step-up method for lower oesophageal sphincter (LOS) localisation.
Methods: A total of 100 patients who underwent 24-hour MII-pH monitoring were enrolled. High-resolution manometry (HRM) was performed before MII-pH monitoring in order to locate the LOS by a different operator. The impedance step-up was defined as an increase of ≥50% with respect to gastric baseline. Lin's concordance correlation coefficient (ρc ) with 95% Bland-Altman limits of agreement (LOA) and Spearman's rho correlation coefficient were used when appropriate.
Results: The median impedance step-up was on average 0.8 cm caudal to the manometric upper border of the LOS. Agreement between two step-up impedance performances and inter-observer agreement were excellent (ρc  = 0.98 and 0.95), although the LOA ranges were wide (-2.4 to 4.0 cm). Impedance step-up performances were similar between patients off and on PPI. Conclusions: We have described an alternative new method for pH impedance probe positioning using impedance step-up. Although less accurate than HRM in locating the LOS, it has excellent intra- and inter-observer agreement. © Author(s) 2019.