Commonly, in clinical practice an automated analysis of pH-MII tracings is obtained.

All pH-MII performed in UZ Brussel are already reviewed manually according to the Wingate con-sensus and interpreted according to the Lyon consensus. In this study, we will prospectively categorise the reasons for discarding reflux episodes identified by automated analysis during the manual review according to the Wingate consensus, as well as the impact on different parameters related to the interpretation of pH-MII. Based on comments received to our retrospective study, we will evaluate possible confounders to the interpretation, including the indication for referral for pH-MII, symptom severity, use of PPI during pH-MII.

Inclusion Criteria:

• Adult patients aged 18 - 80 years old;
• pH-MII performed off PPI

Exclusion Criteria:

• Prior upper GI endoscopy indicative of structural disease (except for oesophagitis or hiatal hernia).
• Incomplete pH-MII (less than 21 hours recording);
• Ph-MII performed on PPI
• Suboptimal quality of the tracings preventing interpretation in clinical practice;
• Prior oesophageal (including anti-reflux intervention) or gastric surgery.

All patients referred for pH-MII are eligible.