Reproducibility of ambulatory intragastric pH monitoring

Ambulatory 24-hour intragastric pH monitoring is nowadays the standard technique for assessing intragastric acidity. For (patho)physiological and pharmacological studies the method has to be sensitive and reproducible. Intragastric acidity was measured continuously by means of intragastric electrodes in the gastric corpus. In order to assess the reproducibility of the test, we repeated it test twice on separate days under standardized conditions in 8 healthy subjects. Subjects were fully ambulatory and no medication was administered. We found no significant difference between 24-hour median pH values during both study days [1.45 (range 1.20-1.90) and 1.40 (1.20-2.00), day 1 and 2, respectively]. There was a significant overall correlation between consecutive 30-min median pH values during 24 hours (r = 0.97, p < 0.0001). Over 24 hours and during the day the technique was able to detect consistent pH changes of > 0.1 pH units, but during the night only changes of > 0.3 pH units could be detected, due to nocturnal pH fluctuations in two subjects. This study shows that ambulatory 24-hour intragastric pH monitoring is reproducible and is able to detect small changes in gastric acidity.