Abstract
Continuous 24-hr intragastric pH-metry was prospectively performed in 801 subjects with different clinical conditions using two pH electrodes placed closely adjacent. The aim was to assess thein situ repeatability of the test and to verify whether the removal of artifacts, interference, and noise usually superimposed onto the fundamental signal recorded by the measuring apparatus improves the clinical usefulness of experimental data. The following debugging/filtering procedure was used: first, pH recordings of each channel were amended separately from artifacts, then they underwent 7 min windowed median interference debugging, and finally Wiener noise filtering was applied. Afterwards, the 24-hr mean pH profile was obtained in each subject by averaging the pH tracings of the two channels every minute (1440 data points/24 hr). The efficiency of this procedure was assessed at each step by evaluating the difference among groups using the O'Brien test, a distribution-free nonparametric method well-suited for evaluating differences among groups allocated onto a two-way layout. The differences among groups calculated from raw pH data of the single channels can be very misleading, in that it is possible to find that they are significant on one channel and not significant on the other channel. Conversely, the significance of the differences among groups increases progressively at each step of the above debugging/filtering procedure applied to raw pH profiles of each channel. Seven minutes was shown to be the most suitable time lag for windowed median removal of interference. The whole procedure increases by 10 up to 108 times the probability of detecting differences among groups, particularly when one rules out pH tracings with a discrepancy time between the two channels which is more than 1 hr over the entire 24-hr period. Our results suggest that removal of artifacts, interference, and noise superimposed onto the endoluminal pH tracings can greatly improve the usefulness of 24-hr intragastric pH-metry in every clinical situation. Moreover, test reliability largely depends on thein situ reproduceability of pH measurements.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
McCloy RF, Vickery JC, Baron JH: Long-term recording and computer analysis of simultaneous gastric and duodenal pH under normal conditions in man. Clin Phys Physiol Meas 1:151–162, 1980
Fimmel CJ, Etienne A, Cilluffo T, von Ritter C, Gasser T, Rey JP, Caradonna-Moscatelli P, Sabbatini PF, Pace F, Buhler HV, Bauerfeind P, Blum AL: Long-term ambulatory gastric pH monitoring: Validation of a new method and effect of H2 antagonists. Gastronterology 88:1842–1851, 1985
Shaker R, Kahrilas PJ, Dodds WJ, Hogan WJ. Oesophageal clearance of small amounts of equal or less than one milliliter of acid. Gut 33:7–10, 1992
Murphy DW, Yuan Y, Castell DO: Does the intraesophageal pH probe accurately detect acid reflux? Simultaneous recording with two pH probes in humans. Dig Dis Sci 34:649–656, 1989
Mela GS, Savarino V, Moretti M, Sumberaz A, Bonifacino G, Zentilin P, Caputo E, Villa G, Celle G: Antimony and glass pH electrodes can be used interchangeably in 24 hour studies of gastric acidity. Dig Dis Sci 36:1473–1481, 1990
Kapur BK, Howlett PJ, Kenyont NG, Lunt MJ, Milles JC, Smallwoods RH, Wilson AJ, Bardhan KD: Continuous 24-hour ambulatory monitoring of intragastric pH in man. Clin Phys Physiol Meas 8:123–132, 1987
Savarino V, Mela GS: Comparison of gastric aspiration and continuous pH monitoring with antimony electrode: Methodological remarks. Dig Dis 8(suppl 1):23–30, 1990
Duroux PH, Emde C, Bauerfeind P, Francis C, Grisel A, Thybaud L, Amstrong D, Depeursing L, Blum AL: The ion sensitive field effect transistor (ISFET) pH electrode: A new sensor for long term ambulatory pH monitoring. Gut 32:240–245, 1991
Whitehead R, Truelove S, Gear MWL: The histological diagnosis of chronic gastritis in fiberoptic gastroscope biopsy specimens. J Clin Pathol 25:1–11, 1972
Savarino V, Mela GS, Scalabrini P, Magnolia MR, DiTimoteo E, Percario G, Celle G: Continuous intragastric pH monitoring: Focus on its reproducibility in duodenal ulcer patients. A preliminary report. Gastroenterol Clin Biol 10:826–830, 1986
Bauerfeind P, Cilluffo T, Fimmel CJ, Emde C, von Ritter C, Kohler W, Gugler A, Gasser T, Blum AL: Does smoking interfere with the effect of histamine H2-receptor antagonists on intragastric acidity in man? Gut 28:549–556, 1987
Savarino V, Mela GS, Zentilin P, Magnolia MR, Scalabrini P, Valle F, Moretti M, Bonifacino G, Celle G: Gastric aspiration versus antimony and glass pH electrodes. A simultaneous comparativein vivo study. Scand J Gastroenterol 24:434–439, 1989
Press WH, Flannery BP, Teukolsky SA, Vetterling WT: Numerical Recipes. The Art of Scientific Computing. Cambridge, Cambridge University Press, 1987
Mela GS, Savarino V, Moretti M, Bonifacino G, Sumberaz A, Zentilin P: Clinical relevance of sampling rate in the characterization and analysis of 24-hour gastric acidity. A report on 413 cases. Scand J Gastroenterol 24:683–687, 1989
O'Brien PC. Procedures for comparing samples with multiple endpoints. Biometrics 40:1079–1087, 1984
O'Brien PC, Shampo MA: Statistical considerations for performing multiple tests in a single experiment. 5. Comparing two therapies with respect to several endpoints. Mayo Clin Proc 63:1140–1143, 1988
Merki HS, Fimmel CJ, Walt RP, Harre K, Röhmel J, Witzel L: Pattern of 24 hour intragastric acidity in active duodenal ulcer disease and in healthy controls. Gut 29:1583–1587, 1988
Mela GS, Savarino V, Caputo E, Sumberaz A, Bonifacino G, Zentilin P. 24-hour gastric pH-metry analysis: Influence of arbitrarily predefined time intervals on the reliability of acidity indexes. Am J Gastroenterol 85:381–384, 1990
Herrera JL, Simpson JK, Maydonovitch CL, Wong RKH: Comparison of stationary versus ambulatory 24-hour pH monitoring recording systems. Dig Dis Sci 33:385–388, 1988
Hampton FJ, MacFayden UM, Mayberry JF: Variations in results of simultaneous ambulatory esophageal pH monitoring. Dig Dis Sci 37:506–512, 1992
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Mela, G.S., Savarino, V., Malesci, A. et al. New method for improving accuracy of 24-hour continuous intragastric pH-metry. Digest Dis Sci 39, 1416–1424 (1994). https://doi.org/10.1007/BF02088043
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF02088043