Inter- and intra-rater agreement of interpretation of functional lumen imaging probe in healthy subjects

Background: The functional lumen imaging probe (FLIP) evaluates esophagogastric junction (EGJ) opening and esophageal contractility. Both post hoc and real-time analyses are possible, but reproducibility and reliability of analysis remain undefined. This study assesses inter- and intra-rater agreement of normative FLIP measurements among novice and experienced users.

Methods: Eight motility experts from different institutions independently evaluated de-identified video recordings from 27 asymptomatic healthy subjects using FLIP. Interpretation methods simulating a post-procedure and a live procedure setting were tested. Novice FLIP users (n = 3) received training prior to post-procedure interpretation. Experienced FLIP users (n = 5) interpreted using both methods. Users recorded maximum EGJ and distal esophageal body diameter, distensive pressure, and EGJ distensibility index (EGJ-DI), at balloon fill volumes of 50-, 60-, and 70 ml, as well as repetitive antegrade contractions (RACs). Inter- and intra-rater agreements of diameters, distensive pressure and EGJ-DI were assessed by intra-class correlation coefficient (ICC) and Pearson's correlation coefficient (PCC). Percentage agreement evaluated inter- and intra-rater reliability for RACs.

Key results: Novice and experienced users acquired normative FLIP metrics. Good-to-excellent inter- and intra-rater reliability were achieved for all variables at 60 ml balloon fill volumes. Median parameters at 60 ml balloon fill volume were as follows: EGJ-DI 5.5 mm² /mmHg, maximum EGJ diameter 18.6 mm, distensive pressure at maximum EGJ diameter 48.1 mmHg, and distal esophageal body diameter 19.5 mm.

Conclusions and inferences: Normative FLIP parameters can be reliably extracted from FLIP videos using both real-time and post hoc analyses, with high reliability between experienced and novice users.