13C-octanoic acid breath test for measurement of solid gastric emptying: reproducibility in normal subjects and patients with diabetes mellitus

Objective To examine the intraindividual reproducibility of the octanoic acid breath test in normal subjects and diabetics and to investigate whether cardiovascular autonomic neuropathy and delayed gastric emptying influence the intraindividual reproducibility.Methods Nine normal subjects (six men, three women,mean age 38 years) and 15 diabetics with insulin treatment [nine men, six women; mean age 47 years; six had cardiovascular autonomic diabetic neuropathy (CADN) and/or delayed gastric emptying time] were, after a nocturnal fasting period, given a standard test meal (labeled with 13C-octanoic acid, 1 046 kJ). Breath samples were taken at ten minute intervals over first one hour and at fifteen minute intervals over the following three hours and examined for 13CO 2 by isotope ratio infrared spectrometry. Using a regression method gastric emptying half times (t 1/2) and lag phase (t lag) were determined.Results There was not a significant difference of t 1/2 and t lag between two measurements in normal subjects and diabetics. The coefficients of variation of day-to-day reproducibility were 11.7% for t 1/2, 19.4% for t lag in normal subjects and 17.8% for t 1/2, 28.2% for t lag in diabetics, but there was not significant difference between normal subjects and diabetics. There was not significant difference of intraindividual coefficient of variation of t 1/2 and t lag between diabetics with/without CADN and between diabetics with normal gastric emptying time and diabetics with delayed gastric emptying time.Conclusions The 13C-octanoic acid breath test has a high intraindividual reproducibility which is not affected by the cardiovascular autonomic neuropathy and delayed gastric emptying. It can be recommended as a non-invasive test for assessing gastric emptying time after a solid test meal in diabetics.