Reason for inconsistency between ph monitoring and impedance in detecting acid gastroesophageal reflux: PH-only events

Abstract

Introduction: Acid reflux events detected by pH and not identified by impedance are called 'pH only events'. We aimed to explain the incidence and the possible reasons of 'pH- only events'.Materials and Methods: The automated multichannel intraluminal impedance (Mil) analysis in 50 cases was investigated. Changes in impedance channels during pH-only acid reflux events were examined and grouped. 1. Events that fail to meet the impedance measurement criteria 2. Events with no change in impedance channels 3. Events that meet the impedance criteria, but do not have signs of reflux 4. Artifact 5. Positive deflection due to air.Results: The number of acid reflux events detected in the Mil records was 1475, the number of acid reflux events detected in the pH meter was 3093, and the number of pH-only acid reflux events was 1736. 56.1% of the acid reflux events were detected by pH meter not identified by MII. The most common reasons for this were events no changes in impedance channels (68%) and other reasons such as positive deflection due to air (14%), and events that could not meet impedance measurement criteria (10%). 8% of pH-only events that met MII criteria, but were not accepted as reflux by MII.Conclusions: There was more than half of acid reflux events detected by pH meter but not identified by MIL The reason of this situation has been not clear. For the correct decision, it is important to evaluate Mil recordings together with pH meter results rather than evaluating automatic analysis alone.