[Bases for the use of information theory in qualitative clinical chemical investigations. Use of information theory in clinical chemical investigations, I].

Using information theory, a model communication channel has been constructed to assess the information gain from the performance of clinical chemical tests, in particular qualitative tests. The construct of the model communication channel is especially clear, and it can be easily adapted to the most varied clinical enquiries. The information theoretical parameters, transinformation and test capacity, are used to characterize the information properties of a clinical chemical test. The calculations necessary for the practical application can (primarily when matrices are used) be performed without difficulty, even by non-mathematicians, using modern table calculators. The procedure is illustrated with many numerical examples, and especially applied to combination of qualitative tests.