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RÉSUMÉ Cette étude visait à contribuer à la compréhension des mécanismes cognitifs du diagnostic en médecine d’urgence, sous l’angle de l’erreur, et à tester la valeur heuristique d’un cadre théorique (Raufaste, 2001) qui prévoit que l’activité diagnostique est optimisée sur trois dimensions : la richesse, la pertinence et la flexibilité. Afin de traduire les spécificités de la médecine d’urgence, le modèle initial a été enrichi de deux dimensions, la synchronisation et la coordination et cinq types d’erreurs spécifiques ont été définis, un par dimension. Trente-trois dossiers d’erreurs médicales avérées ont été utilisés pour le test. Les cinq types d’erreurs sont apparus avec des fréquences, des temporalités et des éléments qui leur sont propres. L’interaction prévue par le cadre théorique entre deux des dimensions a été retrouvée dans les erreurs.

DIAGNOSIS ERROR IN EMERGENCY MEDICINE : APPLICATION OF THE “ RATIONAL ANALYSIS OF WORK SITUATIONS ” MODEL This study aims to empirically examine the existence of several cognitive dimensions of the optimisation of medical diagnosis in Raufaste’s model (2001). Three levels of analysis were distinguished : the “ situational ” level (situational factors), the “ task structure ” level (main steps of the diagnosis task), and the “ performative ” level (cognitive mechanisms underlying process optimisation, and related types of failures). At the performative level, the method called “ Rational Analysis of Work Situations ” (Raufaste, 2001) was applied. Raufaste identified three values : “ Richness ”, which represents the maximisation of the number of pieces of information that can be mobilised to handle the case as accurately as possible ; “ Pertinence ”, which takes into account the limited capacity of the human cognitive system : and the necessity, therefore, to limit processing to relevant facts and hypotheses ; and “ Flexibility ”, which is required when the automatic mechanisms that implement richness and pertinence fail. Two other dimensions are also relevant in seeking to explain optimisation in emergency medicine : synchronisation and coordination. Synchronisation represents the necessity to handle dynamic aspects of the situation, whereas coordination represents the need to handle interpersonal aspects. We analysed thirty patients’ case files with recorded medical errors that occurred in the emergency care unit of a large University hospital. We gathered all the relevant information for each case. The coding of failures that occurred within each file was made by means of discussions among three psychologists. The study’s main findings were as follows : (i) All five types of rationality errors were observed. However, their relative frequencies of occurrence were significantly different. (ii) The relationships that could be predicted a priori between rational values were reflected in the numbers of rationality errors within each file that were actually observed. Thus, there was also a significant negative correlation between richness and pertinence. There was a significant negative correlation between flexibility and pertinence. (iii) Richness, relevance and flexibility errors were not similarly distributed over the different phases of diagnosis.