• 1 Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
  • 2 Digestive Physiology, Hopital E Herriot, Hospices Civils de Lyon, Université de Lyon, Lyon, France
  • 3 Gastroenterology Unit, Department of Surgery, Oncology and Gastroenterology, University of Padova, Padova, Italy
  • 4 Ege University School of Medicine, Izmir, Turkey
  • 5 Department of Gastroenterology & Hepatology, Academic Medical Centre, Amsterdam, The Netherlands
  • 6 Medical University of South Carolina, Charleston, South Carolina, USA
  • 7 Digestive Disease, Universita Campus Bio Medico, Roma, Italy
  • 8 Gastroenterology Unit, University of Pisa, Pisa, Italy
  • 9 Digestive Pathophysiology Unit, Baggiovara Hospital, Modena, Italy
  • 10 Department of Medicine, Chlalongkorn University, Bangkok, Thailand
  • 11 Department of Gaastroenterology, Nippon Medical School Chiba Hokusoh Hospital, Chiba, Japan
  • 12 Gunma University Hospital, Maebashi, Japan
  • 13 Section of Gastroenterology and Hepatology, Department of Medicine and Department of Neurogastroenterology Research, The North Danish Regional Hospital, Hjørring, Denmark
  • 14 School of Medical Sciences, Universiti Sains Malaysia, Kota Bharu, Malaysia
  • 15 Cardiac Vascular Sentral Kuala Lumpur, Kuala Lumpur, Malaysia
  • 16 Division of Medical Physiology, Walter Sisulu University, Mthatha, South Africa
  • 17 Gastropenterology, Center of Excellence in Neurogastroenterology and Motility, Department of Medicine, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
  • 18 Translational Research Center for Gastrointestinal Disorders, Katholieke Universiteit Leuven, Leuven, Belgium
  • 19 Immunology and Gastroenterology Departments, Instituto de Investigacion Sanitaria del Hospital Clínico San Carlos (IdISSC), Madrid, Spain
  • 20 Hospital de Alta Complejidad El Cruce, Buenos Aires, Argentina
  • 21 Department of Gastroenterology, University of Veracruz, Veracruz, Mexico
  • 22 Department of Internal Medicine, Sahlgrenska University Hospital, Gothenburg, Sweden
  • 23 Clinical and Experimental Medicine, University of Leuven, Leuven, Belgium
  • 24 University Clinics for Visceral Surgery and Medcine, Bern University Hospital, Bern, Switzerland
  • 25 Experimental Surgery, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, Mexico City, Mexico
  • 26 Department of Gastroenterology, The First Affiliated Hospital of Sun Yat-Sen University, Guangzhou, China
  • 27 Department of Gastroenterology, Bordeaux University Hospital, Bordeaux, France
  • 28 Division of Gastroenterology, Washington University School of Medicine, St. Louis, Missouri, USA
Gut, 2020 Oct 09.
PMID: 33037054 DOI: 10.1136/gutjnl-2020-322627


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.

* Title and MeSH Headings from MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.