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New normal metrics should be used to assess gastroesophageal reflux, researchers say

Reuters Health - 26/11/2020 - New normal values for esophageal impedance-pH metrics, adjusted for region and testing system, should be used to assess gastroesophageal reflux, researchers say, although some experts remain unconvinced.

"We have finally the best set of normal values using impedance-pH metry after more than 15 years, and we are using this technique for clinical diagnosis," Dr. Daniel Sifrim of Barts and The London School of Medicine and Dentistry told Reuters Health by email.

Ambulatory impedance-pH monitoring is an established approach for investigating esophageal symptoms suspicious for gastroesophageal reflux disease (GERD), but it remains unclear whether measurements obtained using different systems or across world regions are comparable. Moreover, normal values have been based on small groups of healthy volunteers from only one or two countries.

Dr. Sifrim and colleagues analyzed 541 impedance-pH tracings from healthy asymptomatic subjects from Africa, Asia, Europe and North and South America using different hardware/software systems (Diversatek and Laborie) to obtain a new set of normal values.

For esophageal acid-exposure time (AET), the 95th percentile for asymptomatic individuals was 2.8% for Diversatek studies and 5% for Laborie studies. Individuals with AET below these thresholds should be considered to have physiological reflux, the authors say.

For the total number of reflux episodes, the data suggest that asymptomatic individuals with fewer than 55 reflux episodes/24 hours using the Diversatek system or fewer than 78 reflux episodes/24 hours using the Laborie system have physiological reflux, the researchers report in Gut.

There was considerable variability in post-reflux swallow-induced peristaltic wave (PSPW) index, with a significant number of individuals scoring below 50%, suggesting that PSPW cannot be used as a single parameter to define GERD, but must be used together with other metrics, according to the authors.

Mean nocturnal baseline impedance (MNBI) was also problematic: The 5th percentile varied widely across regions and between systems.

When all studies performed worldwide with these two systems were compared, total AET, number of reflux episodes, and MNBI at 5 cm above the lower esophageal sphincter were higher with Laborie than with Diversatek.

Besides system differences, there were regional differences in impedance-pH parameters. With the Diversatek system, esophageal AET was higher in South America compared with other Western countries and Asia; the PSPW index was significantly higher in Western countries; and the MNBI in the distal esophagus was significantly higher in Asia.

Using the Laborie system, esophageal AET was significantly higher in the Netherlands, and distal esophageal MNBI was higher in Asia and South Africa and lower in Turkey.

"Impedance-pH metry is the most sensitive and accurate method to detect gastroesophageal reflux, but its use requires a very good and time-consuming manual analysis of the tracings," Dr. Sifrim said. "From now on, diagnostic labs all over the world will have to use the new metrics based on the region and the system they are using."

Dr. Steven DeMeester from The Oregon Clinic, in Portland, who recently reported that impedance-pH testing of symptomatic patients is best done off acid-suppression therapy, told Reuters Health by email, "These results are only applicable when manual evaluation of the tracing has been performed. In the U.S. and most centers, this is seldom done; only the automated analysis is used."

"Total acid-exposure time has regional and gender differences for normal values," he said. "A much more accurate value that has stood the test of time and been proven accurate in multiple countries and populations is the pH (DeMeester) score which takes into account six parameters measured by the pH-recording device. There is no mention in the study of the differences in pH score between systems and regions. Perhaps the score would be less variable if studied."

"Given the above issues this manuscript and the normal values provided are really not going to be able to be widely implemented and remain unproven in terms of positive and negative predictive values for a GERD diagnosis," Dr. DeMeester said. "A better study would be to take patients with confirmed GERD, based on presence of Barrett's esophagus or LA grade C/D esophagitis, and evaluate impedance-pH in these patients to define abnormal, and take clearly normal people with negative pH test, no hiatal hernia, no esophageal mucosal injury, and no reflux symptoms and use their impedance-pH to define normal values."

"Everyone in between normal and abnormal would be suspect for GERD but not confirmed by impedance-pH testing," he said.

SOURCE: https://bit.ly/3jej8XT Gut, online October 9, 2020.

By Will Boggs MD

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