Comparisons of Alimentary Tract Transit Times among Normal Subjects from Two Multicenter Trials Using SmartPill Wireless pH/Pressure Recording Capsule: Its Clinical Implication

Abstract

Purpose: The SmartPill (SP) wireless pH/pressure recording capsule was approved for assessment of gastric emptying (GET) based on data from a gastroparesis (GP) trial. In a separate study colonic transit time (CTT) measured by SP in patients with chronic constipation (CC) was similar to CTT measured with Sitzmarks. These trials encompassed not only two separate sets of healthy volunteers, but also two different test meals. Aim: To compare GET, small bowel transit time (SBTT), CTT, and whole gut transit time (WGTT) from CC and GP trials utilizing different test meals. Methods: In CC study, 68 (32 F, mean age of 37 y) and in GP trial 50 (22 F, mean age of 35 y) controls were enrolled. While fasting, subjects swallowed the SP with a bar (SmartBar; 260 kcal,) and Sitzmarks capsule in the CC trial; or, with standardized meal (99TcEggbeaters, 255 kcal,), in GP study. The WGTT was measured from the time of ingestion of the SP until an abrupt loss of signal. The time from ingestion to rise of pH exceeding pH 4.0 was defined as GET. A sudden drop of 1 pH unit >5 min. was regarded as an ileo-caecal (I-C) arrival. By subtracting GET from I-C time, SBTT and CTT were determined. Based on statistical analysis with Mann-Whitney Test, results are presented as median and 25%-75% range. Results: The median WGTT in both groups was similar (27.1, 22.1–45.5 hrs, vs. 28.0, 23.2–36.8 hrs range; P= 0.872). The CTT was also similar (20.7, 15.4–38.1 hrs, vs. 18.4, 13.0–27.7 hrs range; P= 0.315). The SBTT in controls from the CC trial was 25% faster (3.5, 2.8–4.4 hrs range) than GP study (4.7, 3.8–6.2 hrs range; P= 0.001). The GET in CC trial was 17% faster (2.9, 2.5–3.8 hrs range) than in GP trial (3.5, 3.0–3.9 hrs range; P= 0.045). Of note: the mean values for GET, SBTT, CTT, and WGTT in both groups were similar. Conclusion: 1. SP technology represents a new test for assessing TT within all segments of the GI tract. 2. The difference in the median values of GET and SBTT is because the data was not normally distributed in CC trial. 3. Our results provide a reference for normal values for the office use of SP in the future where SmartBar will be the standard meal.