Normative values for esophageal functional lumen imaging probe measurements: A meta-analysis

Background: The functional lumen imaging probe (Endoflip™) is increasingly used for evaluation of patients with esophageal symptoms. To improve the interpretation of Endoflip™ in clinical practice, normative values with appropriate cut-off values are required. Methods: Original clinical studies describing Endoflip™ use for measurements of esophageal motility in healthy adults were considered. Meta-analysis was performed based on published values. Results: A total of 17 articles were included in the systematic review, 15 of which were included in the meta-analysis, representing 154 unique subjects. At 40 ml distention, the 5th–95th and 10th–90th percentiles for esophagogastric junction distensibility index (EGJ-DI) were 1.96–10.95 mm2/mmHg and 2.36–8.95 mm2/mmHg, respectively. An EGJ-DI below 2 mm2/mmHg was found in 5.4%, and below 3 mm2/mmHg in 20.1% of healthy subjects. At 50 ml distention, the 5th–95th and 10th–90th percentiles for EGJ-DI are 2.86–10.66 mm2/mmHg and 3.28–9.12 mm2/mmHg, respectively (below 2 mm2/mmHg: 0.6%, 3 mm2/mmHg: 6.3%). The 5th–95th and 10th–90th percentiles for EGJ-DI at 60 ml distention were 3.06–8.14 mm2/mmHg and 3.33–7.18 mm2/mmHg, respectively (below 2 mm2/mmHg: 0.0%, 3 mm2/mmHg: 7%). A clear cut-off for lower values was identified while a large spread in values was observed for upper limits of normal for EGJ-DI for all filling volumes. Conclusions: Given these observations, we recommend using a cut-off of 2 mm2/mmHg for clinical practice, values below can be considered abnormal. Given that 5.4% of the healthy subjects will have an EGJ-DI below 2 mm2/mmHg at 40 ml, we recommend using the 50 and 60 ml distention volumes. The clinical use of an upper limit for normality of EGJ-DI seems questionable.