Discounting the duration of bolus exposure in impedance testing underestimates acid reflux

Namasivayam Vikneswaran, Joseph A. Murray

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


Background: Combined impedance-pH testing (MII) allows for detection of reflux episodes regardless of pH. However impedance-based diagnosis of reflux may not routinely account for duration of the reflux episode. We hypothesize that impedance testing may be less sensitive than pH-testing in detecting acid reflux off therapy as a result of discounting duration of exposure. Methods: Baseline characteristics and reflux parameters of MII studies performed off-anti-secretory medications were analyzed. Studies on acid suppressive medication and those with recording times less than 20h or low baseline impedance were excluded. Results: A total of 73consecutive MII studies were analyzed of which 31 MII studies had elevated acid exposure while 16 were abnormal by impedance criteria. MII testing off-therapy was more likely to be abnormal by pH criteria (percent time pH<4) than impedance criteria (total reflux):[42 vs 22% (p =0.02)]. Acid exposure (percent time pH<4) identified more studies as abnormal than MII-detected acid reflux episodes [42 vs 34% (p<0.01)]. Mean acid clearance time (pH-detected) was significantly longer than median bolus clearance time (impedance-detected) in the total [98.7s vs 12.6s (p<0.01)], upright [58.6s vs 13.1s (p<0.01)], and recumbent positions [136.7s vs 14.2s (p<0.01)] with the greatest difference seen in the recumbent position. The mean ratio of mean acid clearance time (pH-detected) and the median bolus clearance time (impedance-detected) was significantly higher in the recumbent position compared to the upright position [11. vs 5.3 (p=0.01)]. Conclusion: Ambulatory impedance testing underestimates acid reflux compared to esophageal acid exposure by discounting the prolonged period of mucosal contact with each acid reflux episode, particularly in the recumbent position.

Original languageEnglish (US)
Article number60
JournalBMC Gastroenterology
Issue number1
StatePublished - Jun 8 2016


  • Impedance
  • Reflux

ASJC Scopus subject areas

  • Gastroenterology


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