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Observational Study
. 2016 Oct;44(8):890-8.
doi: 10.1111/apt.13777. Epub 2016 Aug 24.

Distal Mean Nocturnal Baseline Impedance on pH-impedance Monitoring Predicts Reflux Burden and Symptomatic Outcome in Gastro-Oesophageal Reflux Disease

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Free PMC article
Observational Study

Distal Mean Nocturnal Baseline Impedance on pH-impedance Monitoring Predicts Reflux Burden and Symptomatic Outcome in Gastro-Oesophageal Reflux Disease

A Patel et al. Aliment Pharmacol Ther. .
Free PMC article

Abstract

Background: Mean nocturnal baseline impedance (MNBI), a novel pH-impedance metric, may be a surrogate marker of reflux burden.

Aim: To assess the predictive value of MNBI on symptomatic outcomes after anti-reflux therapy.

Methods: In this prospective observational cohort study, pH-impedance studies performed over a 5-year period were reviewed. Baseline impedance was extracted from six channels at three stable nocturnal 10-min time periods, and averaged to yield MNBI. Distal and proximal oesophageal MNBI values were calculated by averaging MNBI values at 3, 5, 7 and 9 cm, and 15 and 17 cm respectively. Symptomatic outcomes were measured as changes in global symptom severity (GSS, rated on 100-mm visual analogue scales) on prospective follow-up after medical or surgical anti-reflux therapy. Univariate and multivariate analyses assessed the predictive value of MNBI on symptomatic outcomes.

Results: Of 266 patients, 135 (50.8%) were tested off proton pump inhibitor (PPI) therapy and formed the study cohort (52.1 ± 1.1 years, 63.7% F). The 59 with elevated acid exposure time (AET) had lower composite and distal MNBI values than those with physiological AET (P < 0.0001), but similar proximal MNBI (P = 0.62). Linear AET negatively correlated with distal MNBI, both individually and collectively (Pearson's r = -0.5, P < 0.001), but not proximal MNBI (Pearson's r = 0, P = 0.72). After prospective follow-up (94 patients were followed up for 3.1 ± 0.2 years), univariate and multivariate regression models showed that distal MNBI, but not proximal MNBI, was independently predictive of linear GSS improvement.

Conclusions: Distal oesophageal MNBI negatively correlates with AET and, when assessed off PPI therapy, is independently predictive of symptomatic improvement following anti-reflux therapy.

Figures

Figure 1
Figure 1
MNBI averaged across proximal esophageal channels (top; 15 and 17 cm above the LES) and distal esophageal channels (bottom; 3, 5, 7, and 9 cm above the LES) plotted on the y-axis against AET (from left to right, 25% to 0%) on the x-axis, in patients tested off PPI therapy. When evaluated with Pearson's r, distal MNBI correlated modestly with AET (r=−0.5, p=0.005), but not proximal MNBI (r=−0.03, p=0.72),
Figure 2
Figure 2
Gradient of MNBI in relationship to AET in patients tested off PPI. Box (25th-75th percentile) and whiskers (5th-95th percentile) plots on distal (left) and proximal MNBI values compared between physiologic AET <4%, borderline elevated AET (4-6%) and elevated AET ≥6%. Distal MNBI was significantly lower with elevated AET (p≤0.008 compared to other two groups), but not proximal MNBI (p=0.721); distal MNBI in borderline elevated AET resembled that in physiologic AET (p=ns).
Figure 3
Figure 3
Gradients of MNBI in distal channels in relationship to AET in patients tested off PPI. Box-and-whiskers plots on patients tested off PPI therapy, for individual MNBI values at 3, 5, 7, and 9 cm above the LES compared between physiologic AET <4% and elevated AET ≥6%.; MNBI comparisons were significantly different between these AET groups (p≤0.001 for all comparisons). For AET between 4-6%, distal MBNI values differed from physiologic AET at 3 cm (p=0.03), and from elevated AET≥6% at 5, 7 and 9 cm (p≤0.03) but not other channels (p>0.08).
Figure 4
Figure 4
Forest plots for univariate and multivariate linear regression models of independent predictors of linear GSS improvement in patients tested off PPI therapy. Prediction of linear risk is shown as risk ratios, with bars representing 95% confidence intervals; values not crossing the zero axis are significant (asterisks). *p=0.014 and 0.035 for distal MNBI and p=0.009 and p=0.020 for impedance SAP in univariate and multivariate models, respectively.

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