Figure 1.

Study recruitment flowchart.

Of 2113 potential participants, 832 met the GERD case group criteria. Among them, 449 had an RDQ score ⩾12 and a positive PPI test, and 383 had a positive esophageal endoscopy. The non-GERD group included 686 patients with RDQ scores <12 and negative esophageal endoscopy. Patients with data analysis difficulties due to data loss or incomplete data were excluded.

GERD, gastroesophageal reflux disease; PPI, proton pump inhibitor; RDQ, reflux disease questionnaire.