An expert panel-based study on recognition of gastro-esophageal reflux in difficult esophageal pH-impedance tracings

Reflux Testing: Wireless pH, Impedance-pH, and Mucosal Impedance

Reflux-like symptoms are common; however, not always due to gastro-esophageal reflux disease (GERD) and thus objective testing for GERD is critical, particularly prior to long-term or invasive therapy. In the absence of Los Angeles Grades B, C, or D esophagitis on upper endoscopy, ambulatory reflux monitoring off antisecretory therapy with either a 96-h prolonged wireless reflux monitoring or 24-h pH-impedance is recommended. Mucosal impedance testing is an emerging adjunct technology to assess esophageal mucosal integrity. These testing modalities can help establish the presence or absence of proven GERD, and ultimately guide antireflux-targeted treatments.

Optimizing ambulatory reflux monitoring: current findings and future directions

INTRODUCTION

Gastroesophageal reflux disease (GERD) is the most common diagnosis seen in outpatient gastroenterology clinics. The diagnosis is made by a variable combination of symptoms, response to acid suppressive therapy, endoscopic evaluation, and pH testing. In this review, we evaluate how to utilize various reflux testing in clinical practice based on current evidence.

AREAS COVERED

Ambulatory reflux monitoring is a recognized diagnostic tool for clinical decision making in patients with/without established GERD, persistent reflux symptoms, and lack of response to proton pump inhibitor (PPI) therapy. Standard evaluation approaches include 24-hour pH or impedance monitoring via transnasal catheter, prolonged (48 to 96 hour) wireless pH monitoring, and the recently developed mucosal integrity testing. Testing using one of these methods allows for measurement of acid exposure, frequency of reflux, and to phenotype patients to personalize treatment recommendations.

EXPERT OPINION

The primary goal of future studies should be to simplify ambulatory reflux monitoring, reduce diagnostic latency, improve patient tolerance, and to obtain clinical outcomes-based studies. The current paradigm of reflux testing is vastly complex with multiple modalities and shifting cutoffs of pH abnormality that lead to high economic burden on the society.

Manual censoring of impedance tracings by the Wingate consensus reduces the number of impedance episodes, impacting on reflux categorization

BACKGROUND

The Lyon consensus classifies the evidence of gastroesophageal reflux (GERD) based on endoscopic features and results of pH/impedance monitoring (pH-MII) including the post-reflux swallow-induced peristaltic wave index (PSPWI) and mean nocturnal baseline impedance (MNBI). The Wingate consensus established criteria to reduce inter-reviewer variability when assessing reflux episodes and PSPWI by impedance. This study aims to assess the influence of the Wingate criteria on the different pH-MII parameters obtained by automated analysis.

METHODS

Thirty consecutive pH-MII off PPI were reviewed according to Wingate criteria. Number of impedance episodes and PSPWI were compared before and after censoring from automatic analysis. Reflux categorization according to Lyon consensus between censored and uncensored data was compared. Pearson correlations between impedance parameters and censored episodes were calculated.

KEY RESULTS

Censoring the tracings significantly reduced the number of reflux episodes (66 [42-90.25] vs. 44.5 [21.5-61.5], p = 0.0105). Reasons for censoring were as follows: 1/ anterograde episode: 9.5 [6-13], 2/ impedance drop <50%: 1 [0-3], 3/ duration <4 s: 1 [0-2], 4/ <2 distal channels: 2.5 [1-4], and 5/ artifacts: 2 [1-5]. Censored episodes were in majority non-acid (16.5 [13-26.5] vs. 2 [0-4], p < 0.00001). Censoring altered the categorization of impedance episodes (<40 episodes, 6 vs. 13 for resp. uncensored vs. censored tracings, 40-80 episodes: 13 vs. 13, and >80 episodes: 11 vs. 4, p = 0.0264), but not the symptom index, the symptom association probability, or the categorization according to the Lyon consensus. Nevertheless, individual tracings were affected. The percentage of censored episodes was inversely correlated with the number of acidic impedance episodes (r = -0.62, p = 0.0002).

CONCLUSION AND INFERENCES

Manual interpretation of impedance tracings based on the Wingate consensus reduces the number of impedance episodes, impacting on reflux categorization. Acidic reflux episodes are less likely to be censored, harboring a potential at improving automatic pH-MII analysis.

Application of Artificial Intelligence in Measuring Novel pH-Impedance Metrics for Optimal Diagnosis of GERD

Novel metrics extracted from pH-impedance monitoring can augment the diagnosis of gastroesophageal reflux disease (GERD). Artificial intelligence (AI) is being widely used to improve the diagnostic capabilities of various diseases. In this review, we update the current literature regarding applications of artificial intelligence in measuring novel pH-impedance metrics. AI demonstrates high performance in the measurement of impedance metrics, including numbers of reflux episodes and post-reflux swallow-induced peristaltic wave index and, furthermore, extracts baseline impedance from the entire pH-impedance study. AI is expected to play a reliable role in facilitating measuring novel impedance metrics in patients with GERD in the near future.

Artificial intelligence facilitates measuring reflux episodes and postreflux swallow-induced peristaltic wave index from impedance-pH studies in patients with reflux disease

BACKGROUND/AIM

Reflux episodes and postreflux swallow-induced peristaltic wave (PSPW) index are useful impedance parameters that can augment the diagnosis of gastroesophageal reflux disease (GERD). However, manual analysis of pH-impedance tracings is time consuming, resulting in limited use of these novel impedance metrics. This study aims to evaluate whether a supervised learning artificial intelligence (AI) model is useful to identify reflux episodes and PSPW index.

METHODS

Consecutive patients underwent 24-h impedance-pH monitoring were enrolled for analysis. Multiple AI and machine learning with a deep residual net model for image recognition were explored based on manual interpretation of reflux episodes and PSPW according to criteria from the Wingate Consensus. Intraclass correlation coefficients (ICCs) were used to measure the strength of inter-rater agreement of data between manual and AI interpretations.

RESULTS

We analyzed 106 eligible patients with 7939 impedance events, of whom 38 patients with pathological acid exposure time (AET) and 68 patients with physiological AET. On the manual interpretation, patients with pathological AET had more reflux episodes and lower PSPW index than those with physiological AET. Overall accuracy of AI identification for reflux episodes and PSPW achieved 87% and 82%, respectively. Inter-rater agreements between AI and manual interpretations achieved excellent for individual numbers of reflux episodes and PSPW index (ICC = 0.965 and ICC = 0.921).

CONCLUSIONS

AI has the potential to accurately and efficiently measure impedance metrics including reflux episodes and PSPW index. AI can be a reliable adjunct for measuring novel impedance metrics for GERD in the near future.

Novel Advanced Impedance Metrics on Impedance-pH Testing Predict Lung Function Decline in Idiopathic Pulmonary Fibrosis

INTRODUCTION

Gastroesophageal reflux has been associated with idiopathic pulmonary fibrosis (IPF). Mean nocturnal baseline impedance (MNBI) is a marker of esophageal mucosal integrity, whereas postreflux swallow-induced peristaltic wave (PSPW) index reflects esophageal chemical clearance. Both metrics offer novel ways to assess reflux burden on multichannel intraluminal impedance-pH testing (MII-pH), but their role in extraesophageal reflux remains unclear. We aimed to evaluate the relationship between these novel metrics and lung function decline in patients with IPF.

METHODS

Adults with IPF undergoing prelung transplant MII-pH were enrolled. All patients completed pulmonary function testing (PFT) at the time of MII-pH and at the 1-year follow-up. MNBI was calculated by averaging baseline impedance at three 10-minute intervals (1 AM/2 AM/3 AM). PSPW index was the proportion of all reflux episodes, followed by a peristaltic swallow within 30 seconds. Univariate (Student t-test/Pearson correlation) and multivariable (general linear regression) analyses were performed.

RESULTS

One hundred twenty-five subjects (mean age = 61.7 years, 62% men) were included. Forced expiratory volume in one second and forced vital capacity declined more significantly over 12 months in subjects with lower distal MNBI, proximal MNBI, and PSPW index (all P < 0.05). On multivariable analyses adjusting for age, sex, proton pump inhibitor use, and baseline lung function, distal MNBI (β = -10.86, P = 0.024; β = -8.03, P = 0.045), proximal MNBI (β = -13.5, P = 0.0068; β = -9.80, P = 0.025), and PSPW index (β = -18.1, P = 0.010; β = -12.55, P = 0.050) remained predictive of greater forced expiratory volume in one second and forced vital capacity decline.

DISCUSSION

Low distal MNBI, proximal MNBI, and PSPW index independently predicted more severe lung function decline over 1 year in patients with IPF. These impedance metrics may have prognostic value and support a role for reflux in IPF pathogenesis.

Episode-level reflux characteristics: How experienced reviewers differentiate true reflux from artifact on pH-impedance studies

BACKGROUND

Accurate reflux episode identification is crucial for pH-impedance interpretation. Individual reflux episode characteristics associated with inter-reviewer concordance are incompletely understood.

METHODS

Ambulatory pH-impedance studies from 19 GERD patients (median age 52 years, 78.9% F) were analyzed by 5 reviewers. Metadata from pH-impedance studies were exported to a dedicated software tool designed to compare episode-by-episode identification between reviewers within a ±7.5 s window. Patient position, acidic vs. nonacidic episodes, acid clearance time (ACT), bolus clearance time (BCT), and proximal extent of reflux episodes were compared between episodes identified by all reviewers against those identified by automated analysis, and one to four reviewers, respectively.

RESULTS

Automated analysis identified 1644 episodes (median 78 episodes per patient, IQR 64-108), of which 84.9% were identified by ≥3 reviewers and 57.1% by all reviewers; 339 unique episodes were added by at least 1 reviewer. Characteristics defining 5 reviewer concordance included acid reflux episodes (88.9%), upright episodes (88.4%), high proximal extent (median 17 cm, IQR 15-17 cm), and longer acid clearance times (67.0 s, IQR 29.0-146.0 s) (P < 0.001 compared to 1-4 reviewer concordance for each). In contrast, 1 reviewer-identified episodes were 69.8% acidic, 76.9% upright, and limited to the distal esophagus. Using 5-reviewer concordance, designation of GERD evidence changed from automated analysis in 16%-19% of patients.

CONCLUSIONS

Acidic episodes with high proximal extent in the upright position and longer acid clearance times on pH-impedance studies have the highest concordance for identification by expert reviewers. Reflux episode identification may be influenced by reviewer opinion despite availability of established criteria.

Inter-reviewer Variability in Interpretation of pH-Impedance Studies: The Wingate Consensus

Ambulatory pH-impedance monitoring evaluates gastroesophageal reflux disease (GERD) symptoms that persist despite empiric treatment trials.¹ Although automated analysis of pH-impedance monitoring is known to overestimate non-acid reflux episodes,² even experts may disagree on individual reflux episodes,^3,4 and accurate identification of postreflux swallow-induced peristaltic wave (PSPW). We hypothesized that a formal consensus meeting between expert pH-impedance reviewers would establish definitive criteria for identification of reflux episodes and PSPW, and improve inter-reviewer variability.

Normal values and regional differences in oesophageal impedance-pH metrics: a consensus analysis of impedance-pH studies from around the world

OBJECTIVE

Limitations of existing impedance-pH thresholds include small sample size of normative studies, inclusion of artefactual pH drops and incorrect identification of impedance reflux events. We aimed to obtain new impedance-pH thresholds from expert consensus analysis of tracings from a large number of healthy subjects.

DESIGN

Of 541 studies performed worldwide using two different systems (Diversatek, USA, and Laborie, Netherlands), 150 tracings with oesophageal diagnoses, behavioural disorders and study-related artefacts were excluded. The remainder studies were subject to two reviewer consensus analysis, in-person or through video conference, consisting of editing meals and pH drops, identification of impedance reflux and postreflux swallow-induced peristaltic wave (PSPW) using strict pre-established criteria and measurement of distal mean nocturnal baseline impedance (MNBI).

RESULTS

Consensus analysis was performed in 391 tracings (age 32.7 years, range 18-71, 54.2% female). Normative thresholds were significantly different between Diversatek and Laborie (total acid exposure time: 2.8% and 5%; reflux episodes: 55 and 78; MNBI at 3 cm: 1400 and 1500 ohms, at 5 cm: 1400 and 1800 ohms). Males had higher acid exposure, more reflux episodes and lower MNBI. Significant regional differences were identified, including higher PSPW scores in Western countries, and higher MNBI in Asia using Diversatek, and higher acid exposure in the Netherlands, higher MNBI in Asia and South Africa, and lower MNBI in Turkey using Laborie.

CONCLUSION

Normal impedance-pH monitoring thresholds have regional and system-related differences. Clinical interpretation needs to use normal thresholds valid for the system used and world region, following careful editing of the tracings.

Extraesophageal syndrome of gastroesophageal reflux: relationships with lung disease and transplantation outcome

Gastroesophageal reflux disease (GERD) is prevalent and may be associated with both esophageal and extraesophageal syndromes, which include various pulmonary conditions. GERD may lead to pulmonary complications through the "reflux" (aspiration) or "reflex" (refluxate-triggered, vagally mediated airway spasm) mechanisms. While GERD may cause or worsen pulmonary disorders, changes in respiratory mechanics due to lung disease may also increase reflux. Typical esophageal symptoms are frequently absent and objective assessment with reflux monitoring is often needed for diagnosis. Impedance monitoring should be considered in addition to traditional pH study due to the involvement of both acidic and weakly acidic/nonacidic reflux. Antireflux therapy may improve outcomes of some pulmonary complications of GERD, although careful selection of a candidate is paramount to successful outcomes. Further research is needed to identify the optimal testing strategy and patient phenotypes that would benefit from antireflux therapy to improve pulmonary outcomes.

Esophageal pH-impedance monitoring in children: position paper on indications, methodology and interpretation by the SIGENP working group

Multichannel intraluminal impedance pH (MII-pH) monitoring currently represents the gold standard diagnostic technique for the detection of gastro-esophageal reflux (GER), since it allows to quantify and characterize all reflux events and their possible relation with symptoms. Over the last ten years, thanks to its strengths and along with the publication of several clinical studies, its worldwide use has gradually increased, particularly in infants and children. Nevertheless, factors such as the limited pediatric reference values and limited therapeutic options still weaken its current clinical impact. Through an up-to-date review of the available scientific evidence, our aim was to produce a position paper on behalf of the working group on neurogastroenterology and acid-related disorders of the Italian Society of Pediatric Gastroenterology, Hepatology and Nutrition (SIGENP) on MII-pH monitoring technique, indications and interpretation in pediatric age, in order to standardise its use and to help clinicians in the diagnostic approach to children with GER symptoms.

PROLONGED GASTROESOPHAGEAL REFLUX MONITORING BY IMPEDANCE-PHMETRY: A REVIEW OF THE SUBJECT PONDERED WITH OUR EXPERIENCE WITH 1,200 CASES

BACKGROUND

Prolonged monitoring increased our knowledge on gastroesophageal reflux (GER), and the disease became known as gastroesophageal reflux disease (GERD). Prolonged reflux monitoring permits the diagnosis of GERD when endoscopic findings are not enough to characterize it.

OBJECTIVE

The objective of this paper is to review the current knowledge on impedance-pH monitoring, taking into account the published literature and the authors experience with 1,200 exams.

METHODS

The different types of prolonged reflux monitoring, namely: conventional pHmetry, catheter-free pHmetry and impedance-pHmetry will be briefly described. The new possibilities of evaluation with impedance-pHmetry are emphasized, namely: the study of symptomatic patients in use of proton pump inhibitors (PPIs); evaluation of patients with symptoms suggestive of GERD although with normal endoscopy and normal pHmetry, diagnostic elucidation of patients with atypical symptoms or supra-esophageal symptoms, mainly chronic cough, study of patients complaining of belch, differentiating gastric and supra-gastric belching, and the proper work-up before anti-reflux surgery.

RESULTS

When impedance was associated to pH monitoring, an impressive technological evolution became apparent, when compared to pH monitoring alone. The main advantages of impedance-pHmetry are: the ability to detect all types of reflux: acid, non-acid, liquid, gaseous. In addition, other important measurements can be made: the ability of the esophagus in transporting the bolus, the measurement of basal mucosal impedance and the evaluation of primary peristalsis post reflux.

CONCLUSION

Impedance-pHmetry is a promising method, with great advantages over conventional pHmetry. The choice between these two types of monitoring should be very judicious. The authors suggest the importance of careful evaluation of each reflux episode by the physician responsible for the examination, necessary for the correct interpretation of the tracings.

Pediatric Gastroesophageal Reflux Clinical Practice Guidelines: Joint Recommendations of the North American Society for Pediatric Gastroenterology, Hepatology, and Nutrition and the European Society for Pediatric Gastroenterology, Hepatology, and Nutrition

This document serves as an update of the North American Society for Pediatric Gastroenterology, Hepatology, and Nutrition (NASPGHAN) and the European Society for Pediatric Gastroenterology, Hepatology, and Nutrition (ESPGHAN) 2009 clinical guidelines for the diagnosis and management of gastroesophageal reflux disease (GERD) in infants and children and is intended to be applied in daily practice and as a basis for clinical trials. Eight clinical questions addressing diagnostic, therapeutic and prognostic topics were formulated. A systematic literature search was performed from October 1, 2008 (if the question was addressed by 2009 guidelines) or from inception to June 1, 2015 using Embase, MEDLINE, the Cochrane Database of Systematic Reviews and the Cochrane Central Register of Controlled Clinical Trials. The approach of the Grading of Recommendations Assessment, Development and Evaluation (GRADE) was applied to define and prioritize outcomes. For therapeutic questions, the quality of evidence was also assessed using GRADE. Grading the quality of evidence for other questions was performed according to the Quality Assessment of Studies of Diagnostic Accuracy (QUADAS) and Quality in Prognostic Studies (QUIPS) tools. During a 3-day consensus meeting, all recommendations were discussed and finalized. In cases where no randomized controlled trials (RCT; therapeutic questions) or diagnostic accuracy studies were available to support the recommendations, expert opinion was used. The group members voted on each recommendation, using the nominal voting technique. With this approach, recommendations regarding evaluation and management of infants and children with GERD to standardize and improve quality of care were formulated. Additionally, 2 algorithms were developed, 1 for infants <12 months of age and the other for older infants and children.

Comparison of multichannel intraluminal impedance-pH monitoring and reflux scintigraphy in pediatric patients with suspected gastroesophageal reflux

AIM

To evaluate the agreement of multichannel intraluminal impedance-pH monitoring (MII-pHM) and gastroesophageal reflux scintigraphy (GES) for the diagnosis of gastroesophageal reflux disease.

METHODS

Seventy-five consecutive patients with suspected gastroesophageal reflux disease (GERD) underwent 24-h combined MII-pHM recording and one hour radionuclide scintigraphy during the course of the MII-pHM study. Catheters with 6 impedance channels and 1 pH sensor were placed transnasally. Impedance and pH data analysis were performed automatically and manually. For impedance monitoring, reflux was defined as a retrograde 50% drop in impedance, starting distally and propagating retrogradely to at least the next two more proximal measuring channels. Reflux index (RI, percentage of the entire record that esophageal pH is < 4.0) greater than 4.2% for pHM and number of refluxes more than 50 for 24 h for MII were accepted as positive test results. At scintigraphy, 240 frames of 15 seconds duration were acquired in the supine position. Gastroesophageal reflux was defined as at least one reflux episode in the esophagus. After scintigraphic evaluation, impedance-pH recordings and scintigraphic images were evaluated together and agreement between tests were evaluated with Cohen's kappa.

RESULTS

Sufficient data was obtained from 60 (80%) patients (34 male, 56.7%) with a mean age of 8.7 ± 3.7 years (range: 2.5-17.3 years; median: 8.5 years). Chronic cough, nausea, regurgitation and vomiting were the most frequent symptoms. The mean time for recording of MII-pHM was 22.8 ± 2.4 h (range: 16-30 h; median: 22.7 h). At least one test was positive in 57 (95%) patients. According to diagnostic criteria, GERD was diagnosed in 34 (57.7%), 44 (73.3%), 47 (78.3%) and 51 (85%) patients by means of pHM, MII, GES and MII-pHM, respectively. The observed percentage agreements/κ values for GES and pHM, GES and MII, GES and MII-pHM, and MII and pHM are 48.3%/-0.118; 61.7%/-0.042; 73.3%/0.116 and 60%/0.147, respectively. There was no or slight agreement between GES and pHM alone, MII alone or MII-pHM. pH monitoring alone missed 17 patients compared to combined MII-pHM. The addition of MII to pH monitoring increased the diagnosis rate by 50%.

CONCLUSION

No or slight agreement was found among pH monitoring, MII monitoring, MII-pH monitoring and GES for the diagnosis of gastroesophageal reflux disease.

Reflux monitoring in children

Recently, multichannel intraluminal impedance (MII) monitoring was added to the repertoire of tests to evaluate the (patho)physiology of gastroesophageal reflux (GER) in children. Its advantage above the sole monitoring of the esophageal pH lies in the ability of the detection of both acid and nonacid GER and to discern between liquid and gas GER. Currently, combined 24 h pH-MII monitoring is recommended for evaluation of gastro-esophageal reflux disease (GERD) and its relation to symptoms in infants and children, despite the lack of reference values in these age groups. There is new evidence in the current issue of this Journal supporting the role of pH-MII monitoring for the evaluation of children presenting with gastrointestinal symptoms suggestive of GERD and the prediction of the presence of reflux esophagitis. However, several issues should be taken into account when performing pH-MII clinically.