Comparison of stationary vs ambulatory 24-hour pH monitoring recording systems

New method for improving accuracy of 24-hour continuous intragastric pH-metry. Reflections on physiological and pharmacological studies

Continuous 24-hr intragastric pH-metry was prospectively performed in 801 subjects with different clinical conditions using two pH electrodes placed closely adjacent. The aim was to assess the in situ repeatability of the test and to verify whether the removal of artifacts, interference, and noise usually superimposed onto the fundamental signal recorded by the measuring apparatus improves the clinical usefulness of experimental data. The following debugging/filtering procedure was used: first, pH recordings of each channel were amended separately from artifacts, then they underwent 7 min windowed median interference debugging, and finally Wiener noise filtering was applied. Afterwards, the 24-hr mean pH profile was obtained in each subject by averaging the pH tracings of the two channels every minute (1440 data points/24 hr). The efficiency of this procedure was assessed at each step by evaluating the difference among groups using the O'Brien test, a distribution-free nonparametric method well-suited for evaluating differences among groups allocated onto a two-way layout. The differences among groups calculated from raw pH data of the single channels can be very misleading, in that it is possible to find that they are significant on one channel and not significant on the other channel. Conversely, the significance of the differences among groups increases progressively at each step of the above debugging/filtering procedure applied to raw pH profiles of each channel. Seven minutes was shown to be the most suitable time lag for windowed median removal of interference.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of stationary vs ambulatory 24-hour pH monitoring systems in diagnosis of gastroesophageal reflux disease

Twenty-four-hour intraesophageal pH monitoring is presently considered the most reliable diagnostic test for gastroesophageal reflux. Prolonged esophageal pH measurements can be obtained in hospitalized patients with a stationary technique and in ambulant outpatients by means of a portable device; however, there have been no studies that have examined whether the two approaches provide a similar diagnostic accuracy. We performed a prospective study to compare stationary and ambulatory pH-metry in the diagnosis of gastroesophageal reflux. Seventy-seven control subjects and 178 patients with proven gastroesophageal reflux disease were randomized to either ambulant or static pH-metry, which was performed with standard pH electrodes, sensors, and recorders. Reflux events (intraesophageal pH < 4.0) analyzed were: number of episodes; total, upright, and supine reflux time; number of episodes lasting > 5 min; and duration of the longest episode. A composite score of all reflux events according to DeMeester was also calculated. The limits of normality were defined as the 95th percentiles of the control groups. Both controls and patients assigned to either pH monitoring method were comparable. Of 255 studies attempted, 243 (95%) were completed successfully. The results showed similar median values of reflux events for the two control groups and for the two patients groups. Percent total reflux time provided a good separation between normal and abnormal reflux, with a sensitivity of 0.92 for static pH-metry and 0.68 for the ambulant procedure (respective 95th percentiles, 3.4 and 4.6).(ABSTRACT TRUNCATED AT 250 WORDS)

Variations in results of simultaneous ambulatory esophageal pH monitoring

Twenty-four-hour esophageal pH monitoring is regarded as the gold standard investigation for gastroesophageal reflux (GER) (1) and the possibility of an "incorrect" answer, false positive or false negative, is only rarely considered (2). However, when a group of infants in this hospital had such pH studies performed on two consecutive days, considerable differences in the results were found (3). This also had been reported from other centers (4-6). It seems likely that most of the differences were due to true "biological" variability in the amount of GER from day to day, but it remains possible that variation in the accuracy of the equipment in detecting acid reflux was also involved.

Prolonged ambulatory esophageal pH monitoring in the evaluation of gastroesophageal reflux disease

Gastroesophageal reflux disease is a common problem that frequently presents with atypical complaints including nausea, hiccups, globus sensation, chest pain, hoarseness, coughing, or various pulmonary complaints. Diagnosis may be difficult, as these patients often do not have radiographic or endoscopic evidence of esophagitis. In these difficult cases, prolonged esophageal pH monitoring provides an accurate method of quantitating acid reflux parameters and correlating symptoms with reflux episodes in an outpatient setting. Current equipment is compact, durable, and not difficult to use or extremely expensive. Data analysis, with a particular emphasis on acid-exposure time (total, upright, supine), reliably discriminates between abnormal and normal subjects but it is not a perfect "gold standard" for gastroesophageal reflux disease. Indications for esophageal pH monitoring include: (1) atypical symptoms of acid reflux with normal endoscopy, (2) typical reflux symptoms unresponsive to medical therapy, and (3) the follow-up of reflux disease after either medical or surgical therapy. This test is currently performed primarily by gastroenterologists, but we believe many other groups may find this technology helpful. To meet these expanding applications, test refinements are necessary, particularly easier methods of placing the pH probe and better standards for defining abnormal pH parameters in older patients. The future for esophageal pH monitoring is bright. This technology has the potential to do for the diagnosis of gastroesophageal reflux disease what endoscopy has done for the diagnosis of peptic ulcer disease.

Does the intraesophageal pH probe accurately detect acid reflux? Simultaneous recording with two pH probes in humans

Little is known about the accuracy of intraesophageal pH monitoring, ie, do false negatives occur? This study was designed based on the assumption that if two pH probes are placed equidistant from a distal acid source, and the probes measure different values, then one probe might miss acid if it were there alone. We performed 24-hr intraesophageal pH monitoring in 10 patients with gastroesophageal reflux disease, simultaneously placing two pediatric pH probes (probes A and B) 5 cm proximal to the LES in such close proximity that one would expect only small differences in the acid exposure measured by the probes. However, the amount of acid exposure measured by probes A and B differed greatly in some instances. Individual probe performance does not alone account for these differences, since, when pH recordings were reviewed, one probe was as likely to miss acid exposure as the other. These differences would result in a change in the clinical diagnosis in two of 10 patients. Variability in the number of episodes was great and occurred even when there was concordance in percent acid exposure. These data raise questions about the absolute accuracy of the pH probe as the gold standard in the measurement of gastroesophageal reflux.