TEC Assessment Index

Special Report: Wireless Esophageal pH Monitoring*

Assessment Program
Volume 21, No. 2
May 2006

Executive Summary

Background
Gastroesophageal reflux disease (GERD) is a disorder marked by heterogeneity in symptoms, severity, and available treatment options. Esophageal pH recording is a technique used to evaluate certain patients who may have unusual presentations or difficult to treat manifestations of GERD. Traditionally, this has been done using a pH probe placed in the esophagus and attached by wires to recording equipment, usually for a period of 24 hours. A wireless system is now available, in which the pH probe clipped to the esophagus transmits information to a pager-sized receiver worn by the patient. The wireless system may offer better patient comfort.

Evaluating the value of pH monitoring is difficult. First, there is no gold standard diagnostic test for GERD. The ability of pH monitoring to distinguish between clinically defined GERD subjects and normal controls is limited. Without a reference standard, standard measures of sensitivity and specificity cannot be calculated.

Solid evidence linking the use of any type of pH monitoring to improved patient outcomes is lacking. Current practice guidelines endorse the use of pH monitoring in selected patients, but technical reviews accompanying the guidelines acknowledge that there is modest evidence showing that pH monitoring improves patient outcomes.

Objective
This Special Report will provide information relevant to the evaluation of wireless pH monitoring. This Report will summarize information on:

• Diagnostic performance and clinical utility of traditional pH monitoring
• Feasibility of wireless pH monitoring
• Comparison of performance of traditional and wireless pH monitoring

Methods
MEDLINE was searched using the terms "wireless" and "pH monitoring" for the time period up to March 2006. Articles were identified that involved human studies of the wireless pH monitoring system for use in the diagnosis and management of patients with possible GERD. Additionally, article bibliographies and a bibliography updated to January 2006 supplied by the manufacturer of the wireless system were searched.

Results
Several case series show that the device is successfully attached and produces pH readings for 24 to 48 hours in over 90% of attempts. Two studies compared wireless and wired monitoring in terms of patient comfort and found that in most measures, wireless monitoring is judged to be more comfortable. One study assesses test positivity in GERD subjects and normal controls and found that performance was similar to what has been found with wired monitoring. Although one study shows an 88% concordance in diagnosis of GERD when comparing wireless monitoring to simultaneous wired monitoring, it does not demonstrate that wireless monitoring is better than traditional monitoring in diagnosing or managing GERD. The study does not demonstrate that the wireless monitor is more accurate when the tests are discordant. This degree of concordance between the two methods was achieved only after adjusting test thresholds to maximize concordance. Such a post-hoc adjustment of course cannot be done with the device in use in clinical practice. More experimentation with the device on both GERD patients and normal controls will be needed to better establish appropriate test thresholds that optimize clinical utility of the test.

Studies purporting to show improved diagnostic capability of wireless monitoring when used for 48 hours versus 24 hours were fundamentally flawed because there was no gold standard for diagnosis and no control patients were enrolled in the studies.

Conclusions
Thus, the following conclusions appear to apply to wireless monitoring:

• The procedure is successfully performed and produces successful measurement of esophageal acid in a high proportion of cases. The relatively small number of cases reported does not allow for reliable estimation of rare but potentially serious adverse complications.
• Overall, it is more comfortable than traditional wired monitoring.
• Measurements correlate fairly closely to wired monitoring after adjusting test thresholds; however, because of the lack of an established gold standard, even when the two devices are discrepant, it cannot be determined which device is "correct." Also, different studies have produced different cutoff values for a normal test. More data are needed to establish appropriate diagnostic thresholds.
• No studies establish that wireless monitoring is superior to wired monitoring in reaching a GERD diagnosis or optimally managing a patient. There is no evidence linking the use of the wireless device to an improvement in health outcome.

* This Special Report evaluates the available evidence on wireless esophageal pH monitoring. It does not address the question as to whether the TEC criteria are met, primarily because evidence supporting the clinical role of conventional esophageal pH monitoring is limited and because of the lack of a gold standard, it would be difficult to derive meaningful performance data for the use of wireless monitoring in a formal systematic review setting. 

TEC Assessment Index

KEYWORDS: SpecialReports (category); Gastroenterology (category); DiagnosticandMonitoringTests (category); acid; acid reflux; antacids; Barrett's esophagus; correlation; diaphragm; digestive system disorders; dysphagia; endoscopic gastroplication; endoscopic; endoscopy; esophageal adenocarcinoma; esophageal carcinoma; esophageal manometry; esophageal stricture; erosive esophagitis; esophagitis; esophagus; gastroesophageal junction; gastro-oesophageal; gastroesophageal reflux disease; GEJ; GERD; GI; GORD; H2 blockers; heartburn; hiatal hernia; laparoscopic esophageal surgery; laparoscopy; LES; lower esophageal sphincter; manometry; motility agents; mucosal damage; open fundoplication; pH; PPI; probe; proton pump; proton pump inhibitors; recording; reflux; reflux disease; sensitivity; signal; specificity; stomach; stomach acid; surgery; thoracotomy; transesophageal endoscopic treatments; transmitter; wired; wireless