Utility of baseline impedance level measurement in patients with gastroesophageal reflux symptoms

Twenty-four-hour multichannel intraluminal impedance (MII) and pH monitoring is used for detecting reflux episodes in patients with gastroesophageal reflux (GER) disease. However, the clinical significance of baseline impedance levels (BILs) has not been well studied. We aimed to evaluate whether BILs are related to various reflux events or acid-related parameters and to determine whether BILs during specific intervals could be substituted for 24-h BILs.One-hundred forty-two patients GER symptoms underwent 24-h pH/impedance monitoring. We measured pH [(5 cm above the low esophageal sphincter (LES)] and BILs from three sites (3, 5, and 15 cm above the LES).Eighty-one subjects (57.0%) were diagnosed with gastroesophageal reflux disease, and 53 (37.3%) had acid reflux and 28 (19.7%) had nonacid reflux. The 24-h BILs at distal sites were lower in the "reflux" group than in the "no reflux" group (p0.001) and lower in the "acid reflux" group than in the "nonacid reflux" group (p0.001). However, there was no significant difference in 24-h BILs at the proximal site among the "no reflux", "acid reflux", and "nonacid reflux" groups. The interclass correlation coefficient value of 24-h BILs with daytime 6-h BILs was 0.916 (95% CI 0.882-0.940) and that with nighttime 6-h BILs was 0.909 (95% CI 0.871-0.935).BILs are related to GER, especially acid reflux. Location and duration of assessment for BILs needs to be standardized. Six-hour BILs could be substitutes for 24-h BILs. During analysis of MII-pH, more attention should be paid to BILs in the lower esophagus.