Apply pH-impedance and endoscopic data to visualize the GORD diagnostic outcome.
Guidelines & Evidence
Clinical Details
Section 1
When to Use
When to Use
Modern interpretation of esophageal pH and impedance monitoring results
To provide a definitive "Yes/No" diagnosis of pathological Gastroesophageal Reflux Disease (GERD)
Standardizing the threshold for "Acid Exposure Time" (AET) across clinical practices
Philosophy of Lyon
The Lyon Consensus (2018) identifies that physiological reflux is common and that our thresholds must be high enough to select only those patients truly likely to benefit from anti-reflux surgery or PPIs.
Section 2
Formula & Logic
Acid Exposure Time (AET) Thresholds
< 4%
Definitively Normal (Physiological)
4–6%
Borderline / Indeterminate
> 6%
Definitively Abnormal (Pathological GERD)
Secondary Supportive Metrics
01
Number of Reflux Episodes: Abnormal if > 80 per 24 hours (Borderline if 40–80).
02
Mean Nocturnal Baseline Impedance (MNBI): If < 2292 Ω, suggests impaired mucosal integrity (Supportive of GERD).
The 6% AET threshold is a significantly more rigorous "bar" than the previous 4.2% or 4.5% used in older DeMeester scoring. Studies show that patients with AET > 6% have a virtually 100% symptomatic response rate to robotic fundoplication.
Indeterminate Zone (4-6%)
If a patient falls in the 4–6% "Grey" zone, the diagnosis of GERD should NOT be made based on pH alone. You MUST look at secondary markers (MNBI, PSPW) and symptom association (SAP/SI).
Clinical Pearls
LA Grade C or D esophagitis on endoscopy is considered "Definitive" GERD — pH study is not required
Proven Barrett's Esophagus (histology) is considered "Definitive" GERD
For wireless pH (Bravo), the "Day with the worst AET" is often used, but the 6% threshold remains the anchor
Section 4
Next Steps
Diagnostic Integration
01
AET > 6%: GERD confirmed. Plan for fundoplication, LINX, or long-term PPI optimization.
02
AET < 4% + Correlation: Consider "Functional Heartburn" (requires neuromodulators like SSRIs/TCAs).
03
AET 4-6%: Perform Impedance analysis (MNBI) to break the tie.
Complementary Tools
DeMeester Score (Composite)
Symptom Association Probability (SAP)
Los Angeles (LA) Classification for Esophagitis
Section 5
Evidence Appraisal
The Defining Consensus
Modern diagnosis of GERD: the Lyon Consensus.
Gyawali CP et al. • Gut. 2018;67(7):1351-1362. The landmark document resetting GERD diagnostics.
Developed during an international workshop in Lyon, France (Nov 2014), involving 13 global experts in esophageal motility. The goal was to unify the criteria for "Erosive" and "Non-erosive" GERD into a single evidence-based physiology framework.
