The future of 13C-breath tests.

13C-breath tests are widely applied as a tool to investigate metabolic processes and infectious diseases, but most of them have not yet entered into clinical practice. In order to promote the introduction of more 13C-breath tests into clinical routine application we evaluated the tests so far known with respect to some reasonable criteria, which are valued by one of three marks. The sum sigma of these marks is assumed as a measure of the total value of the respective 13C-breath test. In this way we arrived at 10 tests with sigma value of 10 or more points which seem to have an especially high potential to successfully enter into clinical practice. This is particularly true for the 13C-breath tests with urea, aminopyrine, acetate, galactose, caffeine, octanoic acid, and phenylalanine as substrates. Measures are proposed for promoting the clinical application of such tests.