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Original research
Normal values and regional differences in oesophageal impedance-pH metrics: a consensus analysis of impedance-pH studies from around the world
  1. Daniel Sifrim1,
  2. Sabine Roman2,
  3. Edoardo Savarino3,
  4. Serhat Bor4,
  5. Albert J Bredenoord5,
  6. Donald Castell6,
  7. Michele Cicala7,
  8. Nicola de Bortoli8,
  9. Marzio Frazzoni9,
  10. Sutep Gonlachanvit10,11,
  11. Katsuhiko Iwakiri12,
  12. Osamu Kawamura13,
  13. Anne Krarup14,
  14. Yeong Yeh Lee15,16,
  15. Chai Soon Ngiu17,
  16. Eugene Ndebia18,
  17. Tanisa Patcharatraku19,
  18. Ans Pauwels20,
  19. Julio Pérez de la Serna21,
  20. Rosa Ramos22,
  21. Jose Maria Remes-Troche23,
  22. Mentore Ribolsi7,
  23. Alastair Sammon18,
  24. Magnus Simren24,
  25. Jan Tack25,
  26. Radu Tutuian26,
  27. Miguel Valdovinos27,
  28. Yinglian Xiao28,
  29. Frank Zerbib29,
  30. C Prakash Gyawali30
  1. 1Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
  2. 2Digestive Physiology, Hopital E Herriot, Hospices Civils de Lyon, Université de Lyon, Lyon, France
  3. 3Gastroenterology Unit, Department of Surgery, Oncology and Gastroenterology, University of Padova, Padova, Italy
  4. 4Ege University School of Medicine, Izmir, Turkey
  5. 5Department of Gastroenterology & Hepatology, Academic Medical Centre, Amsterdam, The Netherlands
  6. 6Medical University of South Carolina, Charleston, South Carolina, USA
  7. 7Digestive Disease, Universita Campus Bio Medico, Roma, Italy
  8. 8Gastroenterology Unit, University of Pisa, Pisa, Italy
  9. 9Digestive Pathophysiology Unit, Baggiovara Hospital, Modena, Italy
  10. 10Department of Medicine, Chlalongkorn University, Bangkok, Thailand
  11. 11King Chulalongkorn Memorial Hospital, Thai Red Cross, Bangkok, Thailand
  12. 12Department of Gaastroenterology, Nippon Medical School Chiba Hokusoh Hospital, Chiba, Japan
  13. 13Gunma University Hospital, Maebashi, Japan
  14. 14Section of Gastroenterology and Hepatology, Department of Medicine and Department of Neurogastroenterology Research, The North Danish Regional Hospital, Hjørring, Denmark
  15. 15School of Medical Sciences, Universiti Sains Malaysia, Kota Bharu, Malaysia
  16. 16St George and Sutherland Clinical School, University of New South Wales, Sydney, New South Wales, Australia
  17. 17Cardiac Vascular Sentral Kuala Lumpur, Kuala Lumpur, Malaysia
  18. 18Division of Medical Physiology, Walter Sisulu University, Mthatha, South Africa
  19. 19Gastropenterology, Center of Excellence in Neurogastroenterology and Motility, Department of Medicine, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
  20. 20Translational Research Center for Gastrointestinal Disorders, Katholieke Universiteit Leuven, Leuven, Belgium
  21. 21Immunology and Gastroenterology Departments, Instituto de Investigacion Sanitaria del Hospital Clínico San Carlos (IdISSC), Madrid, Spain
  22. 22Hospital de Alta Complejidad El Cruce, Buenos Aires, Argentina
  23. 23Department of Gastroenterology, University of Veracruz, Veracruz, Mexico
  24. 24Department of Internal Medicine, Sahlgrenska University Hospital, Gothenburg, Sweden
  25. 25Clinical and Experimental Medicine, University of Leuven, Leuven, Belgium
  26. 26University Clinics for Visceral Surgery and Medcine, Bern University Hospital, Bern, Switzerland
  27. 27Experimental Surgery, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, Mexico City, Mexico
  28. 28Department of Gastroenterology, The First Affiliated Hospital of Sun Yat-Sen University, Guangzhou, China
  29. 29Department of Gastroenterology, Bordeaux University Hospital, Bordeaux, France
  30. 30Division of Gastroenterology, Washington University School of Medicine, St. Louis, Missouri, USA
  1. Correspondence to Professor Daniel Sifrim, Blizard Institute, Wingate Institute for Neurogastroenterology, Barts and The London School of Medicine and Dentistry, London E12AJ, UK; d.sifrim{at}qmul.ac.uk

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
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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.

  • Patient consent for publication Not required.

  • Ethics approval Institutional Review Board approval was not deemed necessary.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • 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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