Impact of measurement of esophageal acid exposure close to the gastroesophageal junction on diagnostic accuracy and event-symptom correlation: a prospective study using wireless dual pH monitoring.Am J Gastroenterol. 2009 Dec; 104(12):2918-25.AJ
Ambulatory esophageal pH monitoring has limited diagnostic accuracy in patients with gastroesophageal reflux disease (GERD), especially in those with non-erosive reflux disease (NERD). In addition, there is lack of symptom-reflux association in the majority of GERD patients. The aim of this study was to evaluate the impact of measuring acid exposure 1 cm above the gastroesophageal junction (GEJ) on diagnostic accuracy and symptom correlation in GERD patients compared with conventional pH measurements (6 cm above the GEJ) using the wireless pH system.
GERD patients and controls as defined by two validated questionnaires (Gastroesophageal Reflux Questionnaire and Reflux Disease Questionnaire) were prospectively enrolled. Under direct endoscopic vision, two wireless pH capsules (BRAVO, Given Imaging, Yokneam, Israel) were placed 6 and 1 cm, respectively, above the GEJ. Receiver operator characteristic curves were constructed, and symptom indexes were calculated separately for pH measurements at 6-cm (proximal) and 1-cm (distal) locations.
A total of 40 GERD patients (20 erosive esophagitis (EE) and 20 NERD) and 16 controls were analyzed. Sensitivity and specificity of abnormal acid exposure times in GERD were as follows: proximal: 67 and 66%, distal: 60 and 88%; in EE proximal: 75 and 81%, distal: 84 and 92%; and in NERD proximal: 61 and 67%, distal: 58 and 66%, respectively. The proportion of patients with a positive symptom-reflux correlation in GERD was as follows: symptom index (SI): proximal: 35%, distal: 50%; symptom sensitivity index (SSI): proximal: 25%, distal: 5%; and symptom-associated probability (SAP): proximal: 30% and distal: 35%. The higher proportion of patients with a positive SI distally was due to the EE group (EE, proximal: 35% and distal: 65%; NERD, proximal: 35% and distal: 35%).
Compared with the traditional location, measurement of acid reflux 1 cm above the GEJ improved the diagnostic accuracy as well as symptom correlation in EE, but not in NERD patients. Thus, pH monitoring 1 cm above the GEJ for improving the diagnosis of NERD cannot be recommended in clinical practice at this time.