Ambulatory 24-hour esophageal pH monitoring

Abstract

If 24-hour esophageal pH monitoring is to be a useful diagnostic tool, it must reliably discriminate gastroesophageal reflux patients despite daily variations in distal esophageal acid exposure. To address this issue, we studied 53 subjects (14 healthy normals, 14 esophagitis patients, and 25 patients with atypical symptoms) with two ambulatory pH tests performed within 10 days of each other. Intrasubject reproducibility of 12 pH parameters to discriminate the presence of abnormal acid reflux was determined. As a group, the parameters of percent time with pH less than 4 (total, upright, recumbent) were most reproducible (80%). Therefore, a subject was defined as having gastroesophageal reflux disease if at least one of these three values were abnormal. Intrasubject reproducibility for the diagnosis of reflux disease was 89% for the entire sample. Among subsets, the reproducibility was 93% for the normals and esophagitis patients and 84% for the atypical symptom patients. Total percent time with pH less than 4 was the single most discriminate pH parameter (85%) and nearly equaled that of the three combined parameters (89%). The intrasubject variability of this parameter was determined by the mean +/- 2 SD of the relative differences between the two test results for all 53 subjects. Total percent time with pH less than 4 may vary between tests by a factor of 3.2-fold or less (218% higher to 69% lower). We conclude: (1) ambulatory 24-hr esophageal monitoring is a reproducible test for the diagnosis of gastroesophageal reflux disease; and (2) the large intrastudy variability in 24-hr total acid exposure may limit this test's usefulness as a measurement of therapeutic improvement.

Oesophageal pH has a power‐law distribution in control and gastro‐oesophageal reflux disease subjects

“…[1][2][3][4][5][6] The present results provide a rationale for using a particular pH value based on the differences between the frequencies of different pH values in GERD and normal subjects. That is, the present results illustrate that a variety of different pH values can be used to distinguish between normal and GERD subjects and that there is nothing special about pH 4.…”

“…[14][15][16] Many investigators also use pH 4 to identify an oesophageal reflux episode in that the episode is defined as beginning when oesophageal pH £ 4 and ending when pH > 4. [1][2][3][4][5][6] Some, however, have defined a reflux episode as a decrease in oesophageal pH ‡ 1 without specifying what defines the beginning and end of the episode (e.g. Sifrim et al).…”

“…A common summary measure of oesophageal acid exposure is the percentage of the recording period that oesophageal pH £ 4. [1][2][3][4][5][6] Other summary measures include the number and duration of oesophageal reflux episodes determined using pH 4 to define the beginning and end of a reflux episode. [1][2][3][4][5][6] We are unaware of any solid theoretical or pathophysiological basis for selecting pH 4 or any other oesophageal pH value for these assessments.…”

“…[1][2][3][4][5][6] Other summary measures include the number and duration of oesophageal reflux episodes determined using pH 4 to define the beginning and end of a reflux episode. [1][2][3][4][5][6] We are unaware of any solid theoretical or pathophysiological basis for selecting pH 4 or any other oesophageal pH value for these assessments. This is not to say that a particular pH value cannot be used to assess oesophageal acid exposure or define the occurrence of oesophageal reflux episodes, only that there is no clear rationale for selecting a particular pH value.…”

Refractory Heartburn to Proton Pump Inhibitors: Epidemiology, Etiology and Management

“…Relative studies suggest that 17–29% of patients with erosive esophagitis and 48–72% of patients with typical reflux symptoms responding to PPI therapy present with normal pH studies [59,60,61,62,63,64]. In a prospective cross-over study, Franzen et al [65] raised also a dispute regarding the reproducibility of the examination since the results were different (normal vs. abnormal) in 25% of patients, under standardized conditions, within 10 days.…”