Reproducibility and simplification of ¹³C-octanoic acid breath test for gastric emptying of solids

Objective: The accuracy of the ¹³C-octanoic acid breath test is enhanced by breath sampling over 6 h rather than 4 h, but this increases the cost of the test. Our aim was to validate a less costly but accurate sequence of breath sampling for measuring gastric emptying of solids. Methods: We performed the ¹³C-octanoic acid breath test and tested its reproducibility relative to simultaneous scintigraphy in 30 healthy volunteers. Results: There was a significant but weak correlation between t( 1/2 ) measured by the two tests (r(s) = 0.54, p < 0.005), but not between the duration of the lag phase. The differences in the t( 1/2 ) measurements between the tests were different between subjects but were highly reproducible within subjects. Within- and between-subject variations of measurements of gastric emptying with the ¹³C-octanoic acid breath test were not significantly different from the variations observed with scintigraphy. A subset of 11 breath samples collected over 6 h (24 samples) predicted (r² > 0.95) the variables characterizing the cumulative appearance of ¹³CO₂ in breath; these samples were at 35, 50, 95, 110, 140, 155, 215, 245, 260, 290, and 335 min. The accuracy of this subset of sampling times was confirmed in a separate set of breath test samples over 6 h from the same 30 subjects. Conclusions: The ¹³C-octanoic acid breath test for gastric emptying of solids is as reproducible as scintigraphy. A subset of 11 sampling times provides sufficient information to characterize the whole breath-test curve, but the sampling period should be extended to 6 h after dosing.