C octanoic acid breath test

Although scintigraphy, a non-invasive procedure, is usually considered to be the reference technique for measuring gastric emptying in humans, several drawbacks limit its application in routine practice. Expensive equipment is required and access to a nuclear medicine department, and the use of radioactive isotopes (generally Tc and In) can produce low but significant irradiation. It is diYcult to repeat the technique at frequent intervals or to use it with certain patients such as children or pregnant women. However, these disadvantages are not involved when stable isotopes are used. In 1993, Ghoos et al 3 were the first to report a novel technique based on the use of C octanoic acid, a medium chain fatty acid which is rapidly absorbed in the duodenum and metabolised in the liver. 5 Following oxidation, the resulting 13CO2 is excreted into breath at a level which can easily be detected and measured by isotope ratio mass spectrometry. After validation of the C octanoic breath test in healthy subjects, the same authors developed several applications, including pathophysiological and pharmacological studies. However, the test has not been validated on a large scale by other groups. Initial work of Choi et al was less promising, but a recent report from the same team did find a statistically significant correlation between scintigraphy and breath test. The purpose of the international multicentric study reported in abstract 1 was twofold: firstly, to validate the accuracy and reproducibility of the test on a large scale by reference to gastric scintigraphy, regarded as the gold standard; and secondly, to define the reference values for clinical, pharmacological, and pathophysiological studies. To facilitate comparison with the Ghoos study, the mathematical model developed by their group was used, 15 but applied to diVerent European countries including France, Italy, and Germany. Scintigraphic gastric emptying curves were calculated and fitted using a power exponential function (Weibell model) for the solid curves. Results of solid gastric emptying measurements were expressed as half emptying time (t1/2s) as previously reported by Lartigue et al. In abstract 2 a comparison was made of gastric emptying rates with and without an overnight fast and the conclusion was drawn that due to the lack of an apparent circadian rhythm, gastric emptying studies could be done at diVerent times of day. The application of the C octanoic acid breath test to study gastric emptying in the paediatric population is described in abstract 3. The non-invasive nature of the test is ideal for this age group, but further standardisation of test meals and validation of methodology is required. Abstract 4 describes a novel measurement of gastric emptying using H octanoic acid. Deuterium enters the body water pool after oxidation of the substrate and is then slowly eliminated. This method has potential for measuring gastric emptying in addition to another event by a conventional C breath test, such as fat digestion or oro-caecal transit time.