Article Text
Abstract
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.
- impedance-pH monitoring
- acid exposure time
- post reflux swallow-induced peristaltic wave
- reflux episodes
Data availability statement
Data are available on reasonable request. All data relevant to the study are included in the article or uploaded as online supplemental information. All data relevant to the study are included in the manuscript.
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- impedance-pH monitoring
- acid exposure time
- post reflux swallow-induced peristaltic wave
- reflux episodes
Data availability statement
Data are available on reasonable request. All data relevant to the study are included in the article or uploaded as online supplemental information. All data relevant to the study are included in the manuscript.
Footnotes
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Collaborators International Working Group on Normal values for Impedance-pH monitoring: SB, AB, DC, MC, NDB, MF, SG, KI, OK, AK, YYL, EN, CSN, TP, AP, JPdlS, RR, JMR-T, MR, AS, MS, JT, RT, MV, YX, FZ. All members of The International Working Group on Normal values for Impedance-pH monitoring contributed with their Impedance-pH monitoring tracings from healthy asymptomatic subjects.
Contributors DS: study concept, data collection, organisation of Wingate consensus meetings, consensus analysis, drafting and finalisation of manuscript; SR study concept, discussion of diagnostic criteria, consensus analysis, critical review of manuscript; ES: study concept, discussion of diagnostic criteria, consensus analysis, critical review of manuscript; CPG: study concept, discussion of diagnostic criteria, consensus analysis, finalisation of manuscript. International Working Group on Normal values for Impedance-pH monitoring SB, AB, DC, MC, NDB, MF, SG, KI, OK, AK, YYL, EN, CSN, TP, AP, JPdlS, RR, JMR-T, MR, AS, MS, JT, RT, MV, YX, FZ. All members of The International Working Group on Normal values for Impedance-pH monitoring contributed with their Impedance-pH monitoring tracings from healthy asymptomatic subjects.
Funding The study was conducted with financial support from Research Grant DDCH1A3R, Queen Mary University of London, UK.
Competing interests DS receives research grants from Reckitt Benckiser UK, Jinshan Technology China and Alfa Sigma, Italy. SR: consulting Medtronic, research support Diversatek Healthcare, Medtronic; ES: Lecture Fee: Medtronic, Takeda, Janssen, MSD, Abbvie, Malesci; Consulting: Medtronic, Takeda, Janssen, MSD, Reckitt Bencikser, Sofar, Unifarco, SILA, Oftagest. CPG consults for Medtronic, Diversatek, Ironwood, IsoThrive and Quintiles.
Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research.
Provenance and peer review Not commissioned; externally peer reviewed.