What is the purpose of esophageal pH testing?

Purpose of Esophageal pH Testing

Esophageal pH testing is primarily used to quantify the frequency and duration of esophageal acid exposure to diagnose gastroesophageal reflux disease (GERD) and establish a temporal relationship between symptoms and reflux events. 1

Primary Clinical Applications

• Quantification of acid reflux: Measures the frequency and duration of esophageal acid exposure during a study period, with acid exposure conventionally defined as pH <4.0 1
• Symptom correlation: Establishes temporal relationships between specific symptoms (like cough, chest pain, throat symptoms) and reflux episodes 1
• Evaluation of treatment efficacy: Assesses the effectiveness of pharmacologic therapy on acid suppression 1
• Pre-surgical assessment: Confirms excess esophageal acid exposure before antireflux surgery 1

Types of Esophageal pH Monitoring

Conventional Catheter-Based pH Monitoring

• Involves placement of a pH electrode transnasally to measure distal esophageal pH 1
• Provides data on reflux episodes, duration, and reflux index (percentage of time pH <4.0) 1
• Limited by patient discomfort and potential alteration of normal activities during testing 2

Wireless pH Monitoring

• Allows for extended monitoring (48-96 hours) compared to catheter-based systems 1
• Increases diagnostic yield by capturing more reflux events and symptoms 1
• Recommended for patients intolerant of catheter-based monitoring 1
• Should be undertaken for at least 48 hours to increase diagnostic accuracy 1

pH/Impedance Monitoring

• Emerging as the test of choice for detecting both acid and non-acid reflux 1
• Measures volume, speed, and physical length of both anterograde and retrograde esophageal boluses 1
• Particularly valuable for evaluating patients with persistent symptoms despite PPI therapy 1
• Recommended for patients with chest pain, throat or respiratory symptoms not responding to twice-daily PPIs 1

Clinical Indications

• Non-responsive GERD: For patients with symptoms not responding to twice-daily proton pump inhibitors 1
• Atypical symptoms: Evaluation of chest pain, throat or respiratory symptoms suspected to be due to GERD 1
• Post-surgical assessment: For patients with recurrent or persistent reflux symptoms following antireflux surgery 1
• Pulmonary disorders: For patients with idiopathic pulmonary fibrosis, cystic fibrosis, or other pulmonary disorders that might require lung transplantation 1

Limitations and Considerations

• Mounting evidence suggests poor reproducibility of pH testing and a clear continuum between physiologic GER and pathologic GERD 1
• Standard catheter-based testing cannot detect non-acid reflux events 1
• pH monitoring can significantly reduce reflux-provoking activities during testing, potentially affecting test reliability 2
• The degree of abnormality in pH monitoring variables does not directly correlate with symptom severity 1
• When cough is due to GERD, only an average of 29-35% of coughs appear to be induced by GER events during 24-hour monitoring 1

Evolving Role in GERD Diagnosis

• Traditional pH monitoring is losing value as a primary modality for diagnosing pediatric GERD 1
• Combined pH/impedance testing is evolving into the preferred method for detecting temporal relationships between symptoms and both acid and non-acid reflux 1
• For patients with suspected GERD who fit the clinical profile, empiric treatment may be initiated before testing 1
• pH monitoring during therapy is recommended when symptoms don't improve to determine if therapy needs intensification 1

Esophageal pH testing remains a valuable diagnostic tool when used appropriately, particularly for evaluating atypical presentations of GERD and for pre-surgical assessment, though its limitations must be considered when interpreting results 3, 4.