Objectives Previous studies have reported significant day-to-day variability in esophageal acid exposure measured with the Bravo system. The aim of our study is to prospectively assess if a controlled diet during pH monitoring reduces this variability.Methods Esophagogastroduodenoscopy with placement of the Bravo pH capsule was performed in 85 patients with reflux symptoms. Patients were randomized to a pH restricted (n=44) or unrestricted diet (n=41). Distal esophageal acid exposure was monitored for 48 hours and the pH components of the 1st and 2nd 24 hour recordings were compared. Patients were considered to have an abnormal pH test if there was increased esophageal acid exposure on either or both days of monitoring.ResultsThere were significant differences in acid exposure between the first and second days of pH monitoring in the unrestricted diet group (table). Exclusion of the meal period did not eliminate day-to-day variability and did not change any studies from abnormal to normal.ConclusionsRestriction of the diet to pH controlled food and liquids results in significantly less day-to-day variability in acid exposure on a 48 hour Bravo pH study. If an unrestricted diet is used, excluding the meal periods is of no benefit in reducing day-to-day variability.
Comparison between day 1 and day 2 pH recordings in patients with restricted diet, without restricted diet and without restricted diet after exclusion of the meal periods.

	Restricted(p value*)	Not restricted(p value*)	Not restrictedmeal excluded(p value*)
Composite Score	0.41	0.02	0.03
Fraction time pH<4	0.11	0.01	0.03
Fraction time pH<4(upright)	0.2	0.006	0.01
Fraction time pH<4(supine)	0.2	0.33	0.33
Fraction time pH<4(post-prandial)	0.31	0.02	0.02
# of episodes	0.31	0.06	0.32

(*Wilcoxon Signed Rank Test)