[¹³C]octanoic acid breath test for gastric emptying of solids: Accuracy, reproducibility, and comparison with scintigraphy

Background and Aims: Previous work suggested that a breath test using ¹³C accurately measures gastric emptying of solids. Thus, breath test half emptying time (t(1/2)) minus 66 minutes was claimed to estimate accurately t(1/2) by scintigraphy. The aim of this study was to evaluate the accuracy and reproducibility of this breath test in healthy subjects. Methods: Fifteen volunteers (8 men and 7 women; mean age, 41 ± 13 years) underwent simultaneous scintigraphy and [¹³C]octanoic acid breath test. Scans and breath samples were obtained every 15 minutes for 4 and 6 hours, respectively. The breath test was repeated three times within a 3-week period. Results: Parameters from scintigraphy and breath 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 'duration' (samples over 4, 5, or 6 hours) yielded decreasing estimates of the lag phase and t(1/2). Although widely different values were observed in some subjects, repeated breath tests showed a high degree of reproducibility within individuals (mean coefficient of variation, 12%). Conclusions: [¹³C]Octanoic acid breath test for gastric emptying of solids requires further validation before it can substitute for scintigraphy as a diagnostic test, but it seems useful for intraindividual comparisons.