Information theoretical concepts in clinical chemistry: the use of spreadsheet programs for convenient calculation of...

Information theoretical concepts can be used as most valuable tools for evaluating clinical chemical tests. They offer several advantages over the conventional test evaluation by Bayesian concepts. Although long known, information theory has failed to gain widespread acceptance among clinical chemists, probably due to the rather laborious computation of the necessary quantities. To resolve this technical problem, this paper demonstrates how commonly available computer spreadsheet programs can assist in the computation of information theoretical quantities such as the diverse entropies and the information content. Two spreadsheet versions are presented: firstly, a working sheet is developed for information theoretical evaluation of a two-by-two contingency table corresponding to a dichotomous diagnostic problem (e.g., diseased versus non-diseased) and a dichotomous diagnostic test outcome (e.g., normal versus abnormal), and secondly, a working sheet is shown for a more general situation with up to ten diagnostic alternatives and up to ten possible test outcomes. Typical examples for application of these tools are demonstrated.