S917 Ninety-Six-Hour, Ambulatory pH Monitoring Is Not Superior to 48-Hour pH Monitoring in Establishing Pathologic Esophageal Acid Exposure in Patients With GERD Symptoms

Introduction: Ambulatory esophageal pH testing that can last up to 96 hours quantifies esophageal acid exposure time (AET) to accurately diagnose gastroesophageal reflux disease (GERD). There is no consensus on the optimal duration of the pH testing or if prolonged testing improves the diagnostic yield. We aimed to assess if 96-hour-long esophageal pH measurement is superior to 48-hour pH monitoring in diagnosing GERD. Methods: We conducted a retrospective cohort study of consecutive patients who had either undergone a 48-hour or a 96-hour wireless pH test (Bravo) between 2020 and 2025. Records were reviewed for demographics, symptoms, endoscopy findings, pH results over each day, symptom indices (SI) and symptom association probabilities (SAP). A predominant acid exposure pattern was defined as 2 days with pathologic reflux. A single-day positive test for GERD was defined as AET >6%. Our primary aim was to evaluate if 96 hours of pH monitoring diagnosed more GERD, compared to 48 hours of testing. Our secondary aim was to study if an AET >6% showed agreement between the first and second 48 hours of a 96-hour study. Statistical analysis was performed using a 2 tailed Fisher’s exact test. Results: One hundred fifteen patients met the study criteria. The median age was 63 years (range 24-86 years). There were 81 women (70.4%). Sixty-six (57.3%) patients had a high body mass index, 77 (66.9%) had an endoscopically normal esophagus and 105 (91.3%) had a small (0-2 cm) sliding hiatal hernia. Baseline demographics were similar among the study groups including the AET and DeMeester scores. At 24 hours, AET >6 was seen in 31/94 (32.9%); at 48 hours AET >6 was seen in 44/115 (38.2%) patients, and DeMeester Score >14.7 in 52 (45.2%) patients. At 96 hours, AET >6 was seen in 7 (24.1%) DeMeester Score >14.7 in 10/29 (34.4%). Ninety-six-hour pH monitoring was not more likely than 48-hour testing to diagnose GERD by AET >6% (24.1% vs 34.2%; P = 0.19) or by an abnormal DeMeester score (34.4% vs 45.2%; P = 0.40). However, in patients undergoing prolonged testing, of those who were negative (AET <6%) at 48 hours (N = 20), 7 patients (35%) became positive at 72 or 96 hours. Conclusion: Ninety-six-hour esophageal pH monitoring was not more likely than 48-hour testing to diagnose GERD by AET >6% or by an abnormal DeMeester score in our patient cohort. Additional studies with larger patient cohorts are needed.