Direct comparison of impedance, manometry, and pH Probe in detecting reflux before and after a meal

Combining GERD tests allows strengths and weaknesses of each method to be identified in detecting and characterizing reflux (RE). Aim of this study was to compare two methods that measure bolus volume of a refluxant (impedance monitoring (Imp) and manometry (common cavity)) to pH monitoring which measures changes in acid concentration of a refluxant. Nineteen symptomatic GERD patients and 10 normal volunteers were studied before and after a meal. All had 2-hr simultaneous manometry, pH, and Imp (six sites: 3, 5, 7, 9, 15, 17 cm above LES). Reflux by pH was a fall in pH from above to below 4. There were 973 RE's in all subjects, but only 19% were detected simultaneously by all three methods. Imp detected more RE's (96%) than manometry (76%) or pH probe (28%). Imp was the only method to detect 15% (144/973) of RE's, while detection only by pH probe (2%) or manometry (2%) was rare. Most RE's detected by Imp were detected simultaneously by manometry (75%,720/937). Those not detected by manometry were usually in blind spots either in the vulnerable period 2-3 sec after a swallow, during a posture change, or during a Valsalva. Most RE's detected by Imp were not detected by the pH probe. Though most liquid RE's fasting were detected by pH, most liquid postprandial RE's were not, due primarily to weakly acidic rather than superimposed acid RE's. Bolus clearing time by Imp and manometry was nearly identical, while acid clearing was threefold longer than bolus clearing by Imp or manometry. In conclusion, impedance monitoring is better than manometry and pH monitoring in RE detection before and after a meal, and manometry in determining RE composition as liquid or gas. The pH probe measures RE acidity and acid clearing. Simultaneous impedance and pH combines the two methods strengths, and is a powerful tool for reflux detection and characterization.