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Esophageal pH Monitoring

Editor: Franklin Kasmin Updated: 2/6/2023 2:13:46 PM

Introduction

Gastroesophageal reflux disease (GERD) is a common disorder of the gastrointestinal tract that involves the movement of stomach contents into the esophagus or mouth, causing discomfort or complications.[1] Population-based studies have identified GERD as one of the most common upper gastrointestinal (GI) tract disorders, with a prevalence of about 20% in the United States.[2] Patients may present with typical symptoms, including heartburn or regurgitation, or atypical symptoms such as cough, asthma, hoarseness, chronic laryngitis, throat-clearing, chest pain, dyspepsia, and nausea.[3] 

Typically, GERD is diagnosed clinically and treated with a trial of proton-pump inhibitor (PPI) therapy. Relief of heartburn and regurgitation after a 6 to 8 week trial of PPI therapy is a reliable indicator of GERD. This approach has a sensitivity of 78% and a specificity of 54%; hence a negative trial does not rule-out GERD.[4] However, this is a cost-effective approach to diagnosing GERD rather than proceeding directly to endoscopic or alternative diagnostic testing.[5] If patients present with alarm features (i.e., new-onset dyspepsia at age greater than 60, GI bleeding, dysphagia, odynophagia, weight loss, anemia, persistent vomiting), a trial of PPI therapy is not necessary, and the work-up should directly proceed to early endoscopy.[3]

Ambulatory esophageal pH testing is done with a wireless pH capsule or a traditional pH probe and is the gold standard test for GERD diagnosis.[3] Some patients with typical or atypical GERD symptoms have a normal upper endoscopy and normal ambulatory esophageal pH testing but are unresponsive to standard PPI therapy. Ambulatory pH testing does not detect all types of reflux, especially when the refluxate contains little or no acid.[6] It relies on the acidification of intraesophageal pH to less than 4 as a marker for the presence of gastric contents in the esophagus to diagnose gastroesophageal reflux (GER) episodes. Hence, it has limited use in detecting episodes where the pH fails to fall below 4.[7]

A newer technique combining multichannel intraluminal impedance (MII) testing with pH testing allows for the detailed characterization of the refluxate, including its physical and chemical properties.[2] The MII detects the intraluminal bolus movement with the esophagus via strategic placement of a catheter. It can characterize, in combination with pH testing, whether the bolus is composed of liquid, gas, or mixed components as well as its pH.[2]

Specimen Collection

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Specimen Collection

There is no specific specimen that is collected. The study lasts for 24 hours, and once it is complete, the recording unit is returned to the provider. The information is downloaded to a computer, and subsequent data analysis follows using a software system.[8]

Procedures

Patient Protocol[7][8] 

  • Instructed to fast 4 to 6 hours before probe insertion
  • Provided with a diary to record: time of the meal, the content of the meal, time of upright and recumbent periods, time of administration of acid-suppressing medication, time of symptom occurrence
  • No clear guidelines on dietary restrictions exist; it varies from provider to provider
  • Patients are encouraged to continue their usual eating habits or engage in ordinary activities that are known to induce symptoms

Testing On/Off PPI therapy[9][10]

  • The decision to perform testing on or off PPI therapy depends on the indication for testing.
  • If a patient has a known history of GERD that is refractory to treatment, and the indication for MII-pH testing is to diagnose weakly acidic (non-acid) reflux, PPI therapy continues. Usually, patients remain on high-dose acid-suppressive therapy for at least one week before testing and on the day of testing.
  • If it is unclear whether GERD is the cause of a patient’s symptoms, MII-pH testing is done off PPI therapy to detect acid reflux events.

Insertion Technique[7][8]

  • The MII-pH probe placement is transnasally into the esophagus
  • The probes are 2.1 mm in diameter and allow for pH sensors to be placed 5 cm superior to the lower esophageal sphincter (LES) and 10 cm below the LES
  • Impedance measurements are taken at various segments throughout the esophagus with four impedance-measuring segments in the distal esophagus (3, 5, 7, and 9 cm above the LES) and two segments in the proximal esophagus (at 15 and 17 cm above the LES)
  • The testing usually lasts 24 hours, and once the study is complete, the recording unit is returned to the provider
  • There is subsequent data analysis using a software system

Indications

Clinical indications for combined MII-pH testing include[7][9][11][12][13]:

  1. To quantify and characterize gastroesophageal reflux in patients who have had a minimal or lack of response to acid-suppressive therapy with a proton pump inhibitor (PPI) and who have normal endoscopic findings.
  2. To evaluate patients with atypical gastroesophageal reflux symptoms
  3. To evaluate patients with reflux symptoms and achlorhydria (i.e., atrophic gastritis)
  4. To evaluate patients with reflux symptoms after surgical gastrectomy
  5. To evaluate patients with primary postprandial symptoms
  6. To evaluate patients with reflux symptoms and frequent meal ingestion (i.e., infants)

Potential Diagnosis

Types of Reflux[6][14]

  1. Acidic: pH < 4
  2. Weakly acidic: pH 4 to 7
  3. Weakly alkaline: pH >7

Causes

Insufficient Acid Suppression

  • Medication-related factors
    • Poor compliance with PPI timing (i.e., not taking PPI 30-60 minutes before breakfast as instructed), or poor medication adherence.[15]
    • Certain populations of people who have CYP2C19 mutations could be slow or rapid metabolizers of PPIs, which could ultimately affect the duration of action. Rapid metabolizers could classify into the group with “PPI failure.”[16]
  • Residual acid reflux
    • Research has noted residual acid reflux in some patients despite being on PPI therapy. However, some patients respond better to twice daily therapy rather than once-daily therapy. In a retrospective study done on 135 patients with typical GERD symptoms refractory to once or twice daily PPI therapy, results were abnormal in 31% and 4%, respectively.[17]
  • Weakly acidic or alkaline reflux[18][19]
    • Usually occurs in the postprandial period due to transient lower esophageal sphincter relaxation occurring more often following meal-induced gastric fundus distension.
    • Individuals on PPI therapy - the PPI reduces the acidity level in the stomach; however, the patient continues to have reflux due to structural and motility abnormalities. 
    • Individuals off PPI therapy - usually occur when the food contents buffer gastric acid in the postprandial period, and there is transient lower esophageal sphincter relaxation. 

Reflux Hypersensitivity

  • The diagnosis is made when all of the Rome IV criteria are met for the last three months with symptomatic onset at least six months before the diagnosis [20]:
    • Retrosternal symptoms including heartburn or chest pain
    • Normal endoscopy and eosinophilic esophagitis has been ruled out as a cause 
    • Absence of major esophageal motor disorders
    • Reflux events trigger symptoms despite normal acid exposure on pH or pH-impedance monitoring.

Functional Heartburn

  • The diagnosis is made when all of the Rome IV criteria listed below are met for the last three months with symptomatic onset at least six months before diagnosis and at a frequency of at least twice per week.[21] 
    • Burning retrosternal discomfort or pain
    • No symptom relief despite optimal anti-secretory therapy
    • Absence of evidence that GERD or eosinophilic esophagitis is the cause of the symptoms
    • Lack of major esophageal motor disorders (achalasia, esophagogastric junction outflow obstruction, distal esophageal spasm, jackhammer esophagus, absent contractility)

Alternative Diagnosis

  • Achalasia
  • Eosinophilic esophagitis
  • Pill-induced esophagitis
  • Gastroparesis
  • Stricture
  • Malignancy

Normal and Critical Findings

The overall interpretation of the study is based on normal data obtained from healthy volunteers, which serve to establish reference values.[22] Because acid-suppressive therapy alters the ratio of acid versus non-acid reflux episodes in the postprandial period and reduces the total number of reflux episodes, different normal values are utilized when interpreting the total number of reflux episodes “on” and “off” acid-suppressive therapy.[18][23]  

The symptom index and symptom association probability are two indices that help assess the association of a patient’s symptoms with gastroesophageal reflux episodes (acid and non-acid).[24] The symptom index measures the overall strength of the relationship between symptoms and reflux episodes, and the symptom association probability determines whether this relationship is due to chance.[3] 

Symptom index (SI): number of symptoms associated with reflux occurring in the preceding 5-minute interval divided by the total number of symptoms recorded by the patient during the monitoring period.[24]

    • SI greater than 50% is considered a positive test (i.e., more than half of the total number of reflux events was symptomatic). In this case, patients are considered to have symptomatic gastroesophageal reflux on PPI therapy.
    • SI less than 50% is considered to be a negative test. In this case, patients are considered to have persistent symptoms while on PPI therapy due to causes other than gastroesophageal reflux.

Symptom association probability (SAP): the total measuring time divides into two-minute intervals. A contingency table with four fields listed below assesses correlation with the Fisher exact test.[25] 

    • Number of intervals with GER and symptoms
    • Number of intervals with GER without symptoms
    • Number of intervals without GER and with symptoms
    • Number of intervals without both GER and symptoms

A positive SAP (greater than 95%) is considered statistically significant and is interpreted as an adequate temporal association between GER and the recorded symptom.[25]

Interfering Factors

Although MII-pH testing is a great tool to assess and diagnose GERD-related symptoms, there are some limitations and drawbacks to the test.[2]

  • There is a day-to-day variability of the test.[26][27]
  • Assessment of the reflux-symptom correlation uses the SI and SAP indices; however, the validity of these indices is still uncertain.[2]
  • When performing the test off PPI therapy, MII-pH findings are not always able to predict the response to PPIs in patients with typical reflux-related symptoms.[28]
  • The inability to assess the volume of refluxate[8]
  • Difficulty in measuring changes in impedance in patients that have a low baseline impedance (i.e., Barrett esophagus, severe esophagitis, poor esophageal motility)[8]

Complications

Complications of MII-pH testing include bleeding, infection, and trauma to the nasopharynx or esophagus. 

Patient Safety and Education

The procedure is relatively safe; however, the placement of a transnasal catheter may produce some nasopharyngeal discomfort. It may also alter the usual activities of a patient, including food and drink consumption. Despite this, patients are usually able to complete the entire 24-hour examination. Before the procedure, patients should receive counsel on expectations before the day of the examination and how and what to log into a diary.[7][8]

The contraindications for placement of a transnasal MII catheter include prior nasal surgery or trauma, concurrent use of anticoagulants, or coagulopathy. Safety data on the use of impedance in patients with implantable cardiac defibrillators and pacemakers are yet to be studied.[8]

Clinical Significance

In conclusion, MII-pH is a helpful tool to diagnose GERD as it is more accurately able to detect the variances in refluxate composition at various pH levels than pH metering alone. It has a high sensitivity in identifying all types of reflux episodes.[29] This data collection allows the provider to be better equipped with information to personalize treatment for the patient depending on the underlying cause of their symptoms. 

References


[1]

Richter JE,Rubenstein JH, Presentation and Epidemiology of Gastroesophageal Reflux Disease. Gastroenterology. 2018 Jan;     [PubMed PMID: 28780072]


[2]

de Bortoli N,Martinucci I,Bertani L,Russo S,Franchi R,Furnari M,Tolone S,Bodini G,Bolognesi V,Bellini M,Savarino V,Marchi S,Savarino EV, Esophageal testing: What we have so far. World journal of gastrointestinal pathophysiology. 2016 Feb 15;     [PubMed PMID: 26909230]


[3]

Alzubaidi M,Gabbard S, GERD: Diagnosing and treating the burn. Cleveland Clinic journal of medicine. 2015 Oct;     [PubMed PMID: 26469826]


[4]

Numans ME,Lau J,de Wit NJ,Bonis PA, Short-term treatment with proton-pump inhibitors as a test for gastroesophageal reflux disease: a meta-analysis of diagnostic test characteristics. Annals of internal medicine. 2004 Apr 6     [PubMed PMID: 15068979]

Level 1 (high-level) evidence

[5]

Fass R, Empirical trials in treatment of gastroesophageal reflux disease. Digestive diseases (Basel, Switzerland). 2000;     [PubMed PMID: 10729734]


[6]

Sifrim D,Fornari F, Esophageal impedance-pH monitoring. Digestive and liver disease : official journal of the Italian Society of Gastroenterology and the Italian Association for the Study of the Liver. 2008 Mar;     [PubMed PMID: 18082474]

Level 3 (low-level) evidence

[7]

Tutuian R,Castell DO, Clinical Applications of Esophageal Multichannel Intraluminal Impedance Testing. Gastroenterology     [PubMed PMID: 28286455]


[8]

Wang A,Pleskow DK,Banerjee S,Barth BA,Bhat YM,Desilets DJ,Gottlieb KT,Maple JT,Pfau PR,Siddiqui UD,Tokar JL,Song LM,Rodriguez SA, Esophageal function testing. Gastrointestinal endoscopy. 2012 Aug;     [PubMed PMID: 22657403]


[9]

Hirano I, Richter JE, Practice Parameters Committee of the American College of Gastroenterology. ACG practice guidelines: esophageal reflux testing. The American journal of gastroenterology. 2007 Mar:102(3):668-85     [PubMed PMID: 17335450]

Level 1 (high-level) evidence

[10]

Pritchett JM,Aslam M,Slaughter JC,Ness RM,Garrett CG,Vaezi MF, Efficacy of esophageal impedance/pH monitoring in patients with refractory gastroesophageal reflux disease, on and off therapy. Clinical gastroenterology and hepatology : the official clinical practice journal of the American Gastroenterological Association. 2009 Jul;     [PubMed PMID: 19281866]


[11]

Ford CN, Evaluation and management of laryngopharyngeal reflux. JAMA. 2005 Sep 28;     [PubMed PMID: 16189367]


[12]

Oelschlager BK,Quiroga E,Isch JA,Cuenca-Abente F, Gastroesophageal and pharyngeal reflux detection using impedance and 24-hour pH monitoring in asymptomatic subjects: defining the normal environment. Journal of gastrointestinal surgery : official journal of the Society for Surgery of the Alimentary Tract. 2006 Jan;     [PubMed PMID: 16368491]


[13]

Tutuian R,Mainie I,Agrawal A,Adams D,Castell DO, Nonacid reflux in patients with chronic cough on acid-suppressive therapy. Chest. 2006 Aug;     [PubMed PMID: 16899836]

Level 2 (mid-level) evidence

[14]

Sifrim D,Dupont L,Blondeau K,Zhang X,Tack J,Janssens J, Weakly acidic reflux in patients with chronic unexplained cough during 24 hour pressure, pH, and impedance monitoring. Gut. 2005 Apr     [PubMed PMID: 15753524]


[15]

Hungin AP,Rubin G,O'Flanagan H, Factors influencing compliance in long-term proton pump inhibitor therapy in general practice. The British journal of general practice : the journal of the Royal College of General Practitioners. 1999 Jun     [PubMed PMID: 10562747]


[16]

Goldstein JA, Clinical relevance of genetic polymorphisms in the human CYP2C subfamily. British journal of clinical pharmacology. 2001 Oct     [PubMed PMID: 11678778]


[17]

Charbel S,Khandwala F,Vaezi MF, The role of esophageal pH monitoring in symptomatic patients on PPI therapy. The American journal of gastroenterology. 2005 Feb     [PubMed PMID: 15667483]


[18]

Vela MF,Camacho-Lobato L,Srinivasan R,Tutuian R,Katz PO,Castell DO, Simultaneous intraesophageal impedance and pH measurement of acid and nonacid gastroesophageal reflux: effect of omeprazole. Gastroenterology. 2001 Jun     [PubMed PMID: 11375942]


[19]

Blonski W,Vela MF,Castell DO, Comparison of reflux frequency during prolonged multichannel intraluminal impedance and pH monitoring on and off acid suppression therapy. Journal of clinical gastroenterology. 2009 Oct     [PubMed PMID: 19398927]

Level 2 (mid-level) evidence

[20]

Aziz Q,Fass R,Gyawali CP,Miwa H,Pandolfino JE,Zerbib F, Functional Esophageal Disorders. Gastroenterology. 2016 Feb 15     [PubMed PMID: 27144625]


[21]

Yamasaki T,O'Neil J,Fass R, Update on Functional Heartburn. Gastroenterology & hepatology. 2017 Dec     [PubMed PMID: 29339948]


[22]

Shay S,Tutuian R,Sifrim D,Vela M,Wise J,Balaji N,Zhang X,Adhami T,Murray J,Peters J,Castell D, Twenty-four hour ambulatory simultaneous impedance and pH monitoring: a multicenter report of normal values from 60 healthy volunteers. The American journal of gastroenterology. 2004 Jun;     [PubMed PMID: 15180722]

Level 2 (mid-level) evidence

[23]

Zerbib F,Roman S,Bruley Des Varannes S,Gourcerol G,Coffin B,Ropert A,Lepicard P,Mion F, Normal values of pharyngeal and esophageal 24-hour pH impedance in individuals on and off therapy and interobserver reproducibility. Clinical gastroenterology and hepatology : the official clinical practice journal of the American Gastroenterological Association. 2013 Apr;     [PubMed PMID: 23142603]


[24]

Singh S,Richter JE,Bradley LA,Haile JM, The symptom index. Differential usefulness in suspected acid-related complaints of heartburn and chest pain. Digestive diseases and sciences. 1993 Aug;     [PubMed PMID: 8344094]

Level 2 (mid-level) evidence

[25]

Weusten BL,Roelofs JM,Akkermans LM,Van Berge-Henegouwen GP,Smout AJ, The symptom-association probability: an improved method for symptom analysis of 24-hour esophageal pH data. Gastroenterology. 1994 Dec;     [PubMed PMID: 7958686]


[26]

Savarino E,Zentilin P,Frazzoni M,Cuoco DL,Pohl D,Dulbecco P,Marabotto E,Sammito G,Gemignani L,Tutuian R,Savarino V, Characteristics of gastro-esophageal reflux episodes in Barrett's esophagus, erosive esophagitis and healthy volunteers. Neurogastroenterology and motility : the official journal of the European Gastrointestinal Motility Society. 2010 Oct;     [PubMed PMID: 20557468]


[27]

Zentilin P,Dulbecco P,Savarino E,Giannini E,Savarino V, Combined multichannel intraluminal impedance and pH-metry: a novel technique to improve detection of gastro-oesophageal reflux literature review. Digestive and liver disease : official journal of the Italian Society of Gastroenterology and the Italian Association for the Study of the Liver. 2004 Sep;     [PubMed PMID: 15460839]


[28]

Zerbib F,Belhocine K,Simon M,Capdepont M,Mion F,Bruley des Varannes S,Galmiche JP, Clinical, but not oesophageal pH-impedance, profiles predict response to proton pump inhibitors in gastro-oesophageal reflux disease. Gut. 2012 Apr;     [PubMed PMID: 21997546]


[29]

Sifrim D,Castell D,Dent J,Kahrilas PJ, Gastro-oesophageal reflux monitoring: review and consensus report on detection and definitions of acid, non-acid, and gas reflux. Gut. 2004 Jul;     [PubMed PMID: 15194656]

Level 3 (low-level) evidence