Baseline Intraluminal Impedance Measurement During High-Resolution Esophageal Manometry Correlates Poorly With Gastroesophageal Reflux Disease: 2017 Presidential Poster Award

Abstract

Introduction: Intraluminal impedance measurement during pH testing can detect esophageal reflux. Investigators have demonstrated that impedance data obtained at the time of high resolution esophageal manometry (HREM) can discriminate patients with gastroesophageal reflux disease (GERD). Our aim was to assess the reproducibility of these observations. Methods: Patients who had both pH testing (Bravo probe or pH impedance catheter) and HREM from 2002 to 2017 were retrospectively studied. Demographics, pH testing and manometric data were assessed. Baseline impedance was measured over 10 seconds during the landmark period of HREM. GERD patients had an esophageal pH<4 for ≥5% of total study time whereas controls had an esophageal pH<4 for<5%. For a secondary analysis, patients with proton pump inhibitor (PPI) use were analyzed. Patients with a pH<4 for ≥5% of time were considered GERD cases and patients with a pH<4 for<5% of time, off PPI therapy, were controls. Patients whose PPI status was unknown or with pH<4 for<5% of time, on PPI therapy, were excluded. The correlation of pH<4 with baseline impedance was assessed. Results: Fifty-seven patients were studied (Table 1). Males had a higher likelihood of GERD (P=0.048). Impedance did not differ in GERD patients (mean 1.3±0.8) compared to controls (mean 1.8 ± 1.2) (P=0.075) (Figure 1A). Pearson's correlation of impedance to pH<4 was r=-0.09 (P=0.500) (Figure 2A). The ability of impedance to distinguish GERD patients was low [AUC of 65.2% (P=0.026)] (Figure 3A). Youden's index identified a cutoff of 1.055 kOhms (sensitivity 48.5%, specificity 83.3%) (Table 2). In the secondary analysis (38 patients), impedance was not different in GERD patients (mean 1.9±1.2) compared to controls (mean 1.5 ± 0.9) (P=0.237) (Figure 1B). Pearson's correlation of impedance to pH<4 was r=-0.12 (P=0.485) (Figure 2B). Discrimination of GERD patients remained low [AUC=63.7% (P=0.084)] (Figure 3B). Youden's index identified a cutoff of 1.345 kOhms (sensitivity 62.5%, specificity of 71.4%) (Table 2).Figure: Mean baseline high resolution esophageal manometry impedance measurements for gastroesophageal reflux disease patients and controls using (1A) time pH<4 for ≥ 5% of time (P=0.075) and (1B) time pH<4 for ≥ 5% of time and proton pump inhibitor status (P=0.237).Figure: Scatterplot between time pH<4 for ≥ 5% of the time and baseline high resolution esophageal manometry impedance with fitted linear regression line using (2A) time pH<4 for ≥ 5% of time (r=-0.09, P=0.500) and (2B) time pH<4 for ≥ 5% of time and proton pump inhibitor status (r=-.117, P=0.485).Figure: Receiver operator characteristic curves of baseline high resolution esophageal manometry impedance for discrimination of gastroesophageal reflux disease displaying AUC and optimal thresholds using (3A) time pH<4 for ≥ 5% of time (AUC=65.2%, P=0.026), and (3B) time pH<4 for ≥ 5% of time and proton pump inhibitor status (AUC=63.7%, P=0.084).Table: Table. Covariates measured for each patient where GERD cases were diagnosed using pH <4 for ≥5% of total study timeTable: Table. Results of receiver operator characteristic curve analysis for pH<4+proton pump inhibitor statusConclusion: Discriminating GERD patients from controls using baseline manometric impedance does not seem to be successful. This remains the case when PPI therapy is considered. Ultimately, the results in this report do not corroborate the previous literature. The impedance cutoffs found were poorly sensitive. Baseline intraluminal impedance was not a strong predictor of GERD.