Most GERD symptoms are not due to acid reflux in patients with very low 24-hour acid contact times.

Ambulatory esophageal 24-hr pH monitoring is used to diagnose GERD by determining the total acid contact time and/or symptom index (SI). The aim of this study was to compare the relationship between total acid contact times and SI in two groups: patients with very low vs. very high total acid contact times. We reviewed 973 consecutive 24-hr pH studies and compared patients with the lowest and highest 5% of total acid contact times. The low reflux group was significantly younger (median 50 vs. 54 years) and more predominantly female (78 vs. 47%) than the high reflux group. Median total acid contact time was 0.6 and 26.4% in the low and high reflux groups, respectively. The median SI was significantly lower in the low vs. high reflux groups for all symptoms (heartburn, 0 vs. 100%; regurgitation, 20 vs. 100%; cough, 0 vs. 55%; chest pain, 0 vs. 75%; nausea, 0 vs. 100%; and total SI, 12 vs. 86%). In patients with very low total acid contact times, only 12% of symptoms (typical or atypical) are associated with acid reflux, compared to 86% in patients with very high acid contact times. Younger females are overrepresented in the very low reflux, low SI group.