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Since the introduction of 24-h pH testing about a half century ago, the procedure has gained general popularity and has established itself as an important tool in evaluating patients with suspected gastro-oesophageal reflux disease (GERD). While initially praised as the gold standard for diagnosing GERD, over time the clinical value of the pH test has changed primarily due to the recognition of its inherent limitations. Regardless, the tool provides a unique opportunity to assess the extent of oesophageal acid exposure at different levels of the oesophagus and to determine the relationship between patients’ symptoms and acid reflux events.

The role of pH testing in GERD has evolved over the years, the result of the introduction of potent medical antireflux treatment as well as improvement in surgical techniques. Recent studies have shown that the main indications for referrals for pH testing are failure of proton pump inhibitor (PPI) therapy or presurgical evaluation.1, 2 However, the yield of pH testing in evaluating patients who failed PPI therapy appeared to be very low.2

The traditional test that utilizes a pH probe has been shown to be poorly tolerated by a subset of patients who are undergoing pH testing.3 More disconcerting was the effect of the pH probe on patients’ normal daily activities, which may lead to a marked reduction in reflux-provoking activities. However, by miniaturizing the pH test, patients are able to better tolerate the procedure,1 and longer duration of oesophageal pH measurements can be achieved.4 The introduction of the wireless pH capsule resulted in resurgence in the popularity of the technique. Furthermore, the easy placement of the pH capsule after an upper endoscopy increased the utilization of the test by community-based gastroenterologists.

An important contribution of the pH test is the finding that a significant number of patients with non-erosive reflux disease (NERD) have normal oesophageal acid exposure.5 Other intraoesophageal stimuli have been suggested to cause heartburn that is not related to an acid reflux event. They include weakly acidic reflux, duodenogastro-oesophageal reflux, and motor events.6–8 Visceral hypersensitivity has been suggested as an important underlying mechanism for symptoms in these patients, regardless of the type of stimulus.9

In this supplement, we address the evolving role of pH testing in GERD with a series of articles by experts in the field. We discuss the value and type of information generated by intragastric vs. intraoesophageal pH testing. Additionally, we evaluate the new position of the pH test with the introduction of novel techniques that can assess non-acid-related reflux events, such as the intraluminal multichannel impedance and the BilitecTM. We also discuss potential new indications for the pH test in GERD with the introduction of the wireless pH system; this is because studies have demonstrated that the pH capsule improves the quality and the relevance of the data collected. Lastly, we re-evaluate the role of the pH test in atypical/extraoesophageal manifestations of GERD. The latter is an area that remains poorly understood and the use of the pH test in this patient population, either appropriately or inappropriately, is still very common. Recently, the value of the pH test in patients with extraoesophageal manifestations of GERD has been contested.2

The supplement also includes an article that discusses the physiologic and clinical effects of PPIs on acidic or non-acidic reflux. Several recent studies have suggested that PPIs may slow gastric emptying and induce non-acidic and/or duodenogastro-oesophageal reflux.6, 7, 10 The authors of these studies suggest that these clinical effects may explain the relatively high failure rate (30%) of standard-dose PPI in GERD patients.10 The last article in this supplement addresses the role of acid suppression in patients with NERD or functional heartburn; presently, these are the most commonly encountered patients in gastrointestinal (GI) practice, primarily due to their low response rate to PPI treatment. Because PPI failure is most common in GERD patients seen today in GI practice, interest in NERD and functional heartburn patients has markedly increased in recent years.

The pH test has shown adaptability to changes in our current clinical practice and understanding of the disease process; the role of this test in patients suspected of having GERD will continue to evolve. In the future, it is likely that this tool will be incorporated into a new device that is able to provide comprehensive assessment of the different characteristics of the reflux event, of which acid is just one.

Bilitec is a trademark of Medtronic, Inc.

References

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  2. References
  • 1
    Wong WM, Bautista J, Dekel R, et al. Feasibility and tolerability of transnasal/per-oral placement of the wireless pH capsule vs. traditional 24-h oesophageal pH monitoring – a randomized trial. Aliment Pharmacol Ther 2005; 21: 15563.
  • 2
    Charbel S, Khandwala F, Vaezi MF. The role of esophageal pH monitoring in symptomatic patients on PPI therapy. Am J Gastroenterol 2005; 100: 2839.
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  • 3
    Fass R, Hell R, Sampliner RE, et al. Effect of ambulatory 24-h esophageal pH monitoring on reflux-provoking activities. Dig Dis Sci 1999; 44: 22639.
  • 4
    Pandolfino JE, Richter JE, Ours T, et al. Ambulatory esophageal pH monitoring using a wireless system. Am J Gastroenterol 2003; 98: 7409.
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  • 5
    Martinez SD, Malagon IB, Garewal HS, et al. Non-erosive reflux disease (NERD) – acid reflux and symptom patterns. Aliment Pharmacol Ther 2003; 17: 53745.
  • 6
    Vela MF, Camacho-Lobato L, Srinivasan R, et al. Simultaneous intraesophageal impedance and pH measurement of acid and nonacid gastroesophageal reflux: effect of omeprazole. Gastroenterology 2001; 120: 1599606.
  • 7
    Tack J, Koek G, Demedts I, et al. Gastroesophageal reflux disease poorly responsive to single-dose proton pump inhibitors in patients without Barrett's esophagus: acid reflux, bile reflux, or both? Am J Gastroenterol 2004; 99: 9818.
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  • 8
    Fass R, Tougas G. Functional heartburn: the stimulus, the pain, and the brain. Gut 2002; 51: 88592.
  • 9
    Trimble KC, Farouk R, Pryde A, et al. Heightened visceral sensation in functional gastrointestinal disease is not site-specific. Evidence for a generalized disorder of gut sensitivity. Dig Dis Sci 1995; 40: 160713.
  • 10
    Fass R, Shapiro M, Dekel R, et al. Systematic review: proton-pump inhibitor failure in gastro-oesophageal reflux disease – where next? Aliment Pharmacol Ther 2005; 22: 7994.