720 CONVENTIONAL AND SIMPLE METHODS OF MEASURING MEAN NOCTURNAL BASELINE IMPEDANCE SHOW EXCELLENT AGREEMENT

Abstract

Abstract Mean nocturnal baseline impedance (MNBI) is a measurement that shows promise in investigating reflux disease by reflecting esophageal mucosal integrity. The conventional method of measuring MNBI is time-consuming and operator-dependent. A new, simple method of measuring MNBI has been suggested. This study aimed to report MNBI measurements by both conventional and simple methods in a cohort of laryngopharyngeal reflux (LPR) and gastro-esophageal reflux disease (GERD) patients to validate the simple measurement method. Methods 187 patients were divided into LPR (n = 105) or GERD (n = 82) groups by predominant symptom profile, and underwent off-therapy impedance-pH monitoring. MNBI was blindly measured by both conventional and simple methods, and values were correlated. Bland–Altman plots were constructed to assess mean differences and to identify bias between the two measurement methods. Results For the two measurement methods, mean difference in the distal esophagus was −89 (±328) ohms, in the proximal esophagus was −6 (±653) ohms, and in the pharynx was 128 (±577) ohms. There was strong correlation between conventional and simple MNBI values, with r = 0.940 in the distal esophagus, r = 0.463 in the proximal esophagus, and r = 0.712 in the pharynx (all p < 0.001). Conclusion There was excellent agreement between conventional and simple methods of measuring MNBI, with no evidence of proportional bias. Conventional and simple MNBI values correlated excellently in the distal esophagus, and moderately well in the proximal esophagus and pharynx. This study supports the use of the simple method of measuring MNBI to enhance diagnosis of reflux disease.