48-Hour pH Monitoring Increases the Risk of False Positive Studies When the Capsule is Prematurely Passed
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- Iqbal, A., Lee, Y.K., Vitamvas, M. et al. J Gastrointest Surg (2007) 11: 638. doi:10.1007/s11605-007-0142-y
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Ambulatory wireless 48-h esophageal pH monitoring (Bravo Medtronic, Shoreview, MN, USA) has been shown to be more sensitive in detecting abnormal esophageal acid exposure compared with transnasal 24-h pH probes. However, accurate interpretation of the wireless monitoring data is paramount when contemplating surgical intervention for those with gastroesophageal reflux disease. The aim of this study is to evaluate the incidence of false-positive interpretations of this wireless monitoring data secondary to premature transit of the Bravo capsule into the stomach and subsequently into the duodenum prior to the completion of the 48-h study period. We reviewed 100 consecutive Bravo pH studies at our University Esophageal Motility Center. There were 58 women and 42 men included in our evaluation. Premature transit of the Bravo capsule into the stomach and subsequently into the small bowel was defined by a prolonged gastric pH phase with either evidence of alkalinization and no further reflux episodes or loss of communication with the Bravo capsule prior to the end of the 48-h data collection period. Of the 100 patients reviewed, 11% manifested evidence of early passage of the Bravo capsule resulting in a misinterpretation of the data as abnormal acid exposure. The mean time of inaccurate data after transit of the Bravo capsule was 18 h and 42 min. The mean length of time that the capsule was retained in the stomach prior to duodenal passage was 4 h. If the aforementioned data were included in the final interpretation of the study, it yielded a mean DeMeester score of 44.25 with a mean total time of pH <4 of 14.7% per case. Exclusion of the prolonged gastric phase from the final interpretation of each case resulted in a statistically significant reduction in the mean total time the pH <4 (4.33 vs. 14.7%, p < 0.05) and the mean DeMeester score (12.81 vs. 44.25 p < 0.05). The mean time from the initiation of esophageal pH data to the passage of the Bravo capsule into the stomach was 15 h and 22 min. The observation mandates meticulous inspection of the pH tracing by the interpreting physician throughout the entirety of a 48-h study to identify premature transit of the capsule. Tracings that show prolonged acid exposure or loss of communication with the Bravo capsule should be screened for the capsule’s possible early dislodgement and premature advancement into the stomach.