Investigation of Wireless Capsule (SmartPill®) for Colonic Transit: A Comparative Study with Radiopaque Markers in Health and Constipation

Abstract

Purpose: Traditionally, colonic transit time (CTT) has been assessed with radiopaque marker (Sitzmarks® (SZ)) technique. Although useful, it requires radiation and is hindered by poor patient compliance and complex protocols. This multicenter study aimed to simultaneously assess and compare CTT as measured by SmartPill® (SP)-wireless pH and pressure recording capsule with that of Sitzmarks® in constipated (Rome II) and healthy subjects. Methods: After overnight fast, subjects ingested a nutrient bar (260 kcal) followed by a Sitzmarks® (24 markers) and a SmartPill® capsule. Subjects wore a data receiver for 5 days or until SmartPill® was expelled and kept stool diary. Abdominal x-rays were obtained on days 2 & 5. SmartPill® tracing was examined to assess gastric emptying time (GET) (time to rise in pH>4), small bowel transit time (SBTT) (time to cecal entry with >1 pH drop after GET), CTT (time from cecal entry to abrupt temperature drop), and whole gut transit time (WGTT). To account for the known influence of gender and age on CTT, analysis of covariance was used in the statistical examination of SmartPill® CTT. Results: Table (mean ± SEM, *=P< 0.05). 71 constipated (m/f = 8/63) and 83 healthy (m/f = 42/41) subjects participated. CTT, WGTT, day 2 Sitzmarks® transit, and day 5 Sitzmarks® transit were different (P < 0.001) between constipated patients and controls, even after accounting for gender and age. CTT correlations between SmartPill® and% of markers expelled on day 5 were r = 0.59 (P < 0.0001) in patients and r = 0.46 (P < 0.001) in controls. The diagnostic utility of CTT to predict historical diagnosis of constipation was satisfactory with a computed ROC AUC of 0.74. Patients had slower (P < 0.001) GET, slower (P < 0.01) CTT, and slower (P < 0.02) WGTT compared to controls. There were no serious adverse events. Conclusion: SmartPill® is a novel, and more useful technique of assessing CTT. Its transit highly correlates with Sitzmarks®, and it provides comparable data. Additionally, it provides regional information on GET and SBTT. Thus, SmartPill® provides comprehensive data under physiological conditions, on whole gut and regional transit time in health and functional GI disorders.