Supplementary Material for: Wagner-Nelson Analysis to Create “True” Gastric Emptying Curves in 13C Breath Testing: A Pharmacokinetics-based Review

Backgrounds: Breath testing to study gastric emptying (GE) has been criticized that its conventional analysis provides only overall GE velocity (half-emptying time) that is far off from the scintigraphic scale, and it cannot give a whole pattern of time-GE curve comparable to what the scintigraphy expresses (“true” GE). Summary: GE breath tests (GEBT) approximate absorption of the 13C-marker (GE) from pulmonary 13CO2 elimination. The Wagner-Nelson (WN) method has long been used for accurately describing drug absorption based on urinary elimination. Then, GEBT with WN analysis has been reported to provide a time-GE curve comparable to “true” GE of both solid and liquid meals. To handle the WN method properly, attention should be directed to the two assumptions on which the WN method relies; one-compartment model and first-order kinetics. The former is responsible for slight overestimation of “true” GE of liquids. The latter is associated with the necessity of longer sampling time more than 6 h, which could reduce the convenience of GEBT, but a recent study has proposed how to address this problem. Key Messages: The WN method gives complete picture of time-resolved GE curve (and not just lag phase or half-time values) equivalent to what nuclear scintigraphic studies do.