Modified 13C-octanoate breath test and impact of sampling points

In recent years, the C-octanoate breath test has attracted attention as a simple and noninvasive method of assessing gastric emptying of solids. However, practical procedures for test meals, parameters used, and sampling points have not yet been established. Moving toward a more convenient method, here we examined the influences of sampling interval and duration on the C-octanoate breath test performed on 15 healthy subjects using a commercially-available instant cupcake. Breath samples were obtained every 15 minutes within 4 hours, and every 30 minutes in the subsequent 2 hours. Using computer simulation, the time it took for the fitting curve to peak (Tpeak) was calculated in each setting with each interval (15, 30, 60, and 120 minutes) and test duration (3, 4, 5, and 6 hours). When the sampling interval widened over 30 minutes, the difference from the original 6-hour data became larger than 20% of the coefficient of variance. When the sampling duration was shortened to 3 hours, no appropriate fitting curve could be achieved. These results suggest that a sampling duration of 4 hours at 30-minute intervals seems to be suitable for practical use of the test.