[Diagnostic itineraries in primary care: problem setting, selective abduction, heuristics and threshold approach]

This article offers a review of the logical-cognitive components of the diagnostic process with the aim of integrating them, depending on the characteristics of the problem, into a sequential methodological algorithm, including problem solving, circumstantial knowledge, nosographic recognition and subjective probabilistic evaluation. The article traces the diagnostic process of the practical doctor faced with a patient unknown to him, who complains of recently onset symptoms and who consults a primary care doctor or goes to the emergency room. This approach is suitable for the first diagnostic approach in the generalistic setting (including local healthcare contexts and hospital contexts). It is composed of a continuum of cognitive sub-processes in a step-by-step scheme that is articulated as follows: problem setting, selective abduction, heuristics, Bayesian approach to decision making thresholds, and background pathophysiological interpretation.