Day-to-day discrepancy in Bravo pH monitoring is related to the degree of deterioration of the lower esophageal sphincter and severity of reflux disease

Abstract

Background: The Bravo capsule allows monitoring of esophageal acid exposure over a two-day period. Experience has shown that 24-32% of patients will have abnormal esophageal acid exposure detected on only one of the 2 days monitored. This variation has been explained by the effect of endoscopy and sedation. The aim of this study was to assess the day-to-day discrepancy following transnasal placement of the Bravo capsule without endoscopy or sedation and to determine factors related to this variability.

Methods: Bravo pH monitoring was performed by transnasal placement of the capsule in 310 patients. Patients were divided into groups based on the composite pH score: both days normal, both days abnormal and only one of the 2 days abnormal. Lower esophageal sphincter (LES) characteristics were compared between groups.

Results: Of the 310 patients evaluated, 60 (19%) showed a discrepancy between the 2 days. A total of 127 patients had a normal pH score on both days and 123 had an abnormal pH score on both days. Of the 60 patients with a discrepancy, 27 were abnormal the first day and 33 (55%) were abnormal the second day. Patients with abnormal esophageal acid exposure on both days had higher degrees of esophageal acid exposure and were more likely to have a defective LES compared to those with an abnormal score on only one day (35 vs. 83%, p=0.027).

Conclusion: Patients with a discrepancy between days of Bravo pH monitoring have lower esophageal acid exposure. Variability between the 2 days represents early deterioration of the gastroesophageal barrier and indicates less advanced reflux disease.

Fig. 1

Correlation between day 1 and day 2 for A % total time pH <4 and B composite pH score. The Spearman R correlation coefficients were 0.94 (95% CI = 0.93-0.95, p < 0.0001) and 0.83 (95% CI = 0.79-0.86, p < 0.0001), respectively

Fig. 2

Frequency of an abnormal component on the worst day of reflux in patients with a positive score on only one day and those with a positive score on both days. There was a significant difference for each individual component (†p < 0.01,*p < 0.05, Fisher’s exact test)

Fig. 3

The proportion of the patients who had a discrepancy between day 1 and day 2. Patients were divided into ten groups of equal size (31 in each group) based on the composite pH score on day 1, and the percentage of patients with a discrepancy between day 1 and day 2 is plotted. Fifty-one percent of patients with a pH score between 8.7 and 19.3 on the first day had a discrepancy between day 1 and day 2. In contrast, of those who had a pH score of <8.7 or >19.3 on their first day of monitoring, only 11% had a day-to-day discrepancy

Fig. 4

The prevalence of a defective LES in patients with a normal score on both days (17%), an abnormal score on only one day (35%), and an abnormal score on both days (83%) (p < 0.0001 across all three groups)