[C-13]OCTANOIC ACID BREATH TEST FOR GASTRIC-EMPTYING OF SOLIDS - ACCURACY, REPRODUCIBILITY, AND COMPARISON WITH SCINTIGRAPHY

Background & Aims: Previous work suggested that a breath test using C- 13 accurately measures gastric emptying of solids. Thus, breath test h alf emptying time (t(1/2)) minus 66 minutes was claimed to estimate ac curately t(1/2) by scintigraphy. The aim of this study was to evaluate the accuracy and reproducibility of this breath test in healthy subje cts. Methods: Fifteen volunteers (8 men and 7 women; mean age, 41 +/- 13 years) underwent simultaneous scintigraphy and [C-13]octanoic acid breath test. Scans and breath samples were obtained every 15 minutes f or 4 and 6 hours, respectively. The breath test was repeated three tim es within a 3-week period. Results: Parameters from scintigraphy and b reath test were not correlated significantly. Differences of lag phase and t(1/2) between the two tests were highly variable (range for t(1/ 2), -33.1 to 169.6; mean, 48.0 minutes). Increasing breath test ''dura tion'' (samples over 4, 5, or 6 hours) yielded decreasing estimates of the lag phase and t(1/2) Although widely different values were observ ed in some subjects, repeated breath tests showed a high degree of rep roducibility within individuals (mean coefficient of variation, 12%). Conclusion: [C-13]Octanoic acid breath test for gastric emptying of so lids requires further validation before it can substitute for scintigr aphy as a diagnostic test, but it seems useful for intraindividual com parisons.