Improving the analysis of esophageal acid exposure by a new parameter: area under H+.

OBJECTIVES: We aimed to compare the data provided by 24-h continuous esophageal pH monitoring in a group of patients with gastroesophageal reflux disease (GERD) to those from a group of healthy volunteers using both conventional parameters and calculated area under the curve of hydrogen ion activity (AUH+), a new value that describes the true acid exposure, through both duration and depth of acidity changes. METHODS: Thirty healthy controls and 60 patients with GERD (30 symptomatic patients without endoscopic esophagitis or nonerosive GERD and 30 symptomatic patients with Savary I-IV endoscopic esophagitis or erosive GERD) were enrolled in a study based on 24-h pH monitoring to compare reference values by means of receiver operating characteristic (ROC) discriminant analysis. RESULTS: The best ROC cutoff value for nonerosive GERD patients was AUH+ = 103.7 (mmol/L) x min with sensitivity of 76.7% and specificity of 93.3%. The best ROC cutoff value for erosive GERD patients was AUH+ = 114.1 (mmol/L) x min with sensitivity of 100% and specificity of 96.7%. These cutoff values increase the sensitivity by 16.7% for nonerosive GERD patients and 10% for erosive GERD patients when compared to a common parameter such as the percentage of total time pH is <4 with a limit of 4.2%. CONCLUSIONS: AUH+ is a valid quantitative parameter to measure 24-h esophageal acid exposure. It may be a reliable and significant clinical aid because it is a more sensitive test in discriminating negative or positive adult patients with or without esophagitis who are submitted to 24-h esophageal pH monitoring.