[Anonymity in epidemiological surveys: study and initiation of a new method]

The authors propose a system of registering epidemiological data which ensures strict observation of anonymity. Data are made anonymous at the source: the practitioners who possess the medically confidential information themselves compute the code number creating anonymity through a nonreversible calculation formula: it is impossible to work back from the number to the patient's identity, even if one has the formula and powerful computer resources. This method differs from simple data encoding whose key could either be discovered or revealed: it requires neither keys nor a secret but effects a definitive and irreversible transformation. In compliance with the recommendations of the committee on Ethics, of the French "Ordre des Médecins" and of the Law on Data Processing and Liberties, the method was subjected to a double test for reliability, experimental and theoretical.