Association of Mean Nocturnal Baseline Impedance and AFS EGJ Grading With AET-Defined Reflux Burden in Korean Patients.

BACKGROUND AND AIM: Diagnosing gastroesophageal reflux disease (GERD) is challenging in borderline acid exposure time (AET). The Lyon Consensus 2.0 defines AET ≥ 6% as pathological reflux; however, East Asian standards often apply a 4% threshold, creating a diagnostic gray zone. This study evaluated the association of mean nocturnal baseline impedance (MNBI) and hiatal hernia severity using American Foregut Society (AFS) grading with AET-defined reflux burden. METHODS: We retrospectively analyzed 224 patients who underwent esophagogastroduodenoscopy and 24-h pH-impedance testing at a tertiary center (2022-2025). Patients were stratified by AET thresholds (≥ 4% and ≥ 6%) and categorized as groups (≥ 6%, 4%-6%, and < 4%). Clinical, endoscopic, and physiological parameters were compared. RESULTS: Higher AET was associated with increased AFS grades, reflux episodes, DeMeester scores, and acid exposure times and decreased MNBI values. In multivariate models, only MNBI remained an independent predictor of pathological AET at both ≥ 4% (odds ratio [OR] per 100-unit increase, 0.89, p < 0.001) and ≥ 6% thresholds (OR 0.84, p < 0.001). MNBI showed good performance. Exploratory cutoffs were 2268 Ω for AET ≥ 4% (area under the curve [AUC] 0.814) and 1618 Ω for AET ≥ 6% (AUC 0.883). Higher AFS grades were associated with reflux burden. CONCLUSIONS: In this Korean cohort, lower MNBI was independently associated with AET-defined abnormal acid exposure, whereas AFS grading showed a stepwise association with reflux burden. Combined assessment of MNBI and AFS grading may aid physiological characterization of GERD, particularly in patients with borderline AET, although the internally derived MNBI cutoffs require external validation.