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

Abstract

ObjectiveLimitations 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.DesignOf 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).ResultsConsensus 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.ConclusionNormal 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.

Esophageal motility disorders on high‐resolution manometry: Chicago classification version 4.0©

“… Threshold for median IRP in the supine position is 15 mmHg for Medtronic systems and 22 mmHg for Laborie/Diversatek systems (Moderate GRADE, Strong Recommendation) 14–17 Threshold for median IRP in the upright position is 12 mmHg for Medtronic systems and 15 mmHg for Laborie/Diversatek systems (Low GRADE, Strong Recommendation) 16–18 …”

“… Premature contraction: A distal latency shorter than 4.5 seconds, in the setting of a DCI of 450 mmHg•s•cm or greater 16 …”

“…in the setting of a DCI of 450 mmHg•s•cm or greater 16 If the CDP is difficult to determine, a horizontal line can be Temporal association of ineffective contractions with patient symptoms (e.g. dysphagia) supports diagnosis of clinically relevant, abnormal peristaltic function.…”

Patients With Definite and Inconclusive Evidence of Reflux According to Lyon Consensus Display Similar Motility and Esophagogastric Junction Characteristics

“…4 More recently, a publication from an international consortium highlighted that the traditional cutoff of 4.2% was probably overestimated, and when patients have AET values lower than 6% we should pay more attention on the diagnosis. 43 Thus, more data are necessary to confirm the conclusive diagnosis, particularly if surgery is suggested. In keeping, our study suggests that patients with pathological GERD and inconclusive GERD may be similar in terms of HRM pattern, but further data such as the evaluation of other variables (ie, MNBI or post-reflux swallow-induced peristaltic wave [PSPW]) may be helpful in better understanding patients falling in the grey area.…”

ESNM/ANMS consensus paper: Diagnosis and management of refractory gastro‐esophageal reflux disease

“…Abnormal numbers of reflux episodes are a useful metric mostly in borderline AET, albeit not enough by itself to predict response to therapy 161,162 . Although intermediate values of both metrics taken alone are inconclusive for GERD diagnosis, thresholds have been arbitrary defined and consistently differ between centers and world regions 163 . Patients with normal EGD and GERD symptoms can have true NERD on the basis of abnormal AET in 40% of cases, while the remaining may have functional esophageal disorders 8 .…”