[Coding problems in medical information in the framework of the medicalization of the hospital information system].

The authors review the difficulties presented by the description of medical data, on the basis of the french experience with the programme to medicalize the hospital information system. They explain the different steps in preparing a hospital discharge abstract, and the difficulties presented by each one. They particularly stress the phase of hierarchization in choosing the principal diagnosis. They propose some solutions to improve data quality and an approach based on medical practice patterns.