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Assessment of Tandem Measurements of pH and Total Gut Transit Time in Healthy Volunteers.

Mikolajczyk AE, Watson S, Surma BL, Rubin DT - Clin Transl Gastroenterol (2015)

Bottom Line: There was a significant change in pH for AIC (mean difference: -0.45±0.31, P=0.0015) observed across all subjects.This study demonstrates the safety and feasibility of tandem gut transit and pH assessments using the SmartPill device.In healthy individuals and over 24 h, the gut pH profile does not markedly fluctuate in a given region with more variation seen in the colon compared with the small bowel, which has important implications for future physiology and drug delivery studies.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, The University of Chicago Medicine, Chicago, Illinois, USA.

ABSTRACT

Objectives: The variation of luminal pH and transit time in an individual is unknown, yet is necessary to interpret single measurements. This study aimed to assess the intrasubject variability of gut pH and transit time in healthy volunteers using SmartPill devices (Covidien, Minneapolis, MN).

Methods: Each subject (n=10) ingested two SmartPill devices separated by 24 h. Mean pH values were calculated for 30 min after gastric emptying (AGE), before the ileocecal (BIC) valve, after the ileocecal (AIC) valve, and before body exit (BBE). Intrasubject variability was determined by comparing mean values from both ingestions for an individual subject using standard deviations, 95% limits of agreement, and Bland-Altman plots.

Results: Tandem device ingestion occurred without complication. The median (full range) intrasubject standard deviations for pH were 0.02 (0.0002-0.2048) for AGE, 0.06 (0.0002-0.3445) for BIC, 0.14 (0.0018-0.3042) for AIC, and 0.08 (0.0098-0.5202) for BBE. There was a significant change in pH for AIC (mean difference: -0.45±0.31, P=0.0015) observed across all subjects. The mean coefficients of variation for transit time were 12.0±7.4% and 25.8±15.8% for small and large bowels, respectively (P=0.01).

Conclusions: This study demonstrates the safety and feasibility of tandem gut transit and pH assessments using the SmartPill device. In healthy individuals and over 24 h, the gut pH profile does not markedly fluctuate in a given region with more variation seen in the colon compared with the small bowel, which has important implications for future physiology and drug delivery studies.

No MeSH data available.


Bland-Altman plots for the pH values across the two ingestions for each patient at each location. Solid and dashed lines represent mean and 95% confidence limits of the pairwise differences, respectively. There was no evidence of a relationship between magnitude of the pH difference and magnitude of the absolute measurements. I-C, ileocecal valve.
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fig4: Bland-Altman plots for the pH values across the two ingestions for each patient at each location. Solid and dashed lines represent mean and 95% confidence limits of the pairwise differences, respectively. There was no evidence of a relationship between magnitude of the pH difference and magnitude of the absolute measurements. I-C, ileocecal valve.

Mentions: The mean differences in pH values between the two ingestions were −0.14±0.30 for 30 min AGE (P=0.18), −0.22±0.36 for 30 min BIC (P=0.09), −0.45±0.31 for 30 min AIC (P=0.0015), and −0.10±0.58 for 30 min BBE (P=0.62). In regards to AGE and BIC, the CRs are 0.60 and 0.70, respectively, meaning that 95% of the absolute differences in pH in these two locations are expected to be less than the values of these coefficients. It was not appropriate to calculate a repeatability coefficient for AIC because the mean difference is significantly different from zero (as demonstrated above). However, most intrasubject pH differences associated with the AIC landmark are expected to fall within the interval characterized by the 95% LoA (−1.06, 0.16). BBE pH has a slightly higher CR (1.14). There was no evidence of a linear relationship between magnitude of the pH difference and magnitude of the absolute measurements in the Bland-Altman plots (Figure 4). Regression analyses of the relationship between differences and means for the pairs of observed pH values (not shown) did not reveal any evidence of a systematic bias.


Assessment of Tandem Measurements of pH and Total Gut Transit Time in Healthy Volunteers.

Mikolajczyk AE, Watson S, Surma BL, Rubin DT - Clin Transl Gastroenterol (2015)

Bland-Altman plots for the pH values across the two ingestions for each patient at each location. Solid and dashed lines represent mean and 95% confidence limits of the pairwise differences, respectively. There was no evidence of a relationship between magnitude of the pH difference and magnitude of the absolute measurements. I-C, ileocecal valve.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4816255&req=5

fig4: Bland-Altman plots for the pH values across the two ingestions for each patient at each location. Solid and dashed lines represent mean and 95% confidence limits of the pairwise differences, respectively. There was no evidence of a relationship between magnitude of the pH difference and magnitude of the absolute measurements. I-C, ileocecal valve.
Mentions: The mean differences in pH values between the two ingestions were −0.14±0.30 for 30 min AGE (P=0.18), −0.22±0.36 for 30 min BIC (P=0.09), −0.45±0.31 for 30 min AIC (P=0.0015), and −0.10±0.58 for 30 min BBE (P=0.62). In regards to AGE and BIC, the CRs are 0.60 and 0.70, respectively, meaning that 95% of the absolute differences in pH in these two locations are expected to be less than the values of these coefficients. It was not appropriate to calculate a repeatability coefficient for AIC because the mean difference is significantly different from zero (as demonstrated above). However, most intrasubject pH differences associated with the AIC landmark are expected to fall within the interval characterized by the 95% LoA (−1.06, 0.16). BBE pH has a slightly higher CR (1.14). There was no evidence of a linear relationship between magnitude of the pH difference and magnitude of the absolute measurements in the Bland-Altman plots (Figure 4). Regression analyses of the relationship between differences and means for the pairs of observed pH values (not shown) did not reveal any evidence of a systematic bias.

Bottom Line: There was a significant change in pH for AIC (mean difference: -0.45±0.31, P=0.0015) observed across all subjects.This study demonstrates the safety and feasibility of tandem gut transit and pH assessments using the SmartPill device.In healthy individuals and over 24 h, the gut pH profile does not markedly fluctuate in a given region with more variation seen in the colon compared with the small bowel, which has important implications for future physiology and drug delivery studies.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, The University of Chicago Medicine, Chicago, Illinois, USA.

ABSTRACT

Objectives: The variation of luminal pH and transit time in an individual is unknown, yet is necessary to interpret single measurements. This study aimed to assess the intrasubject variability of gut pH and transit time in healthy volunteers using SmartPill devices (Covidien, Minneapolis, MN).

Methods: Each subject (n=10) ingested two SmartPill devices separated by 24 h. Mean pH values were calculated for 30 min after gastric emptying (AGE), before the ileocecal (BIC) valve, after the ileocecal (AIC) valve, and before body exit (BBE). Intrasubject variability was determined by comparing mean values from both ingestions for an individual subject using standard deviations, 95% limits of agreement, and Bland-Altman plots.

Results: Tandem device ingestion occurred without complication. The median (full range) intrasubject standard deviations for pH were 0.02 (0.0002-0.2048) for AGE, 0.06 (0.0002-0.3445) for BIC, 0.14 (0.0018-0.3042) for AIC, and 0.08 (0.0098-0.5202) for BBE. There was a significant change in pH for AIC (mean difference: -0.45±0.31, P=0.0015) observed across all subjects. The mean coefficients of variation for transit time were 12.0±7.4% and 25.8±15.8% for small and large bowels, respectively (P=0.01).

Conclusions: This study demonstrates the safety and feasibility of tandem gut transit and pH assessments using the SmartPill device. In healthy individuals and over 24 h, the gut pH profile does not markedly fluctuate in a given region with more variation seen in the colon compared with the small bowel, which has important implications for future physiology and drug delivery studies.

No MeSH data available.