[Paradigmatic shifts in clinical practice in the the last generation]

Physicians have always used theoretical models (paradigms) to interpret clinical reality, and have changed the prevailing model only when it could no longer satisfy clinical needs. The purpose of this essay is to review some of the paradigmatic changes in clinical reasoning that have occurred since my undergraduate medial education. My training in the 50's was along the bio-medical model that reduced all diseases to structural or biochemical dysfunctions. Within this framework, causes were perceived as leading inevitably rather than probabilistically to their consequences, and chance and ambiguity had a very small role in explication of pathophysiologic mechanisms and in diagnostic reasoning. The doctor-patient relationship was paternalistic and the orientation to extending survival rejected notions of quality of life and involved parsimonious utilization of health care resources. Today however, clinical reasoning has shifted from deductive and deterministic to inductive (evidence-based) and probabilistic. Disease is believed to result from multiple factors rather than from single causes, and there is increasing acceptance of psycho-social factors of disease. Awareness of the confounding effects of false-positive and false-negative tests has changed the attitude to diagnostic evaluation. Terms, such as risk indicators of disease, predictive value of tests and risk-benefit ratio are increasingly used in discussing clinical decisions. We respect the patient's autonomy more than we did in the past, and consider his/her preferences and quality of life in clinical decision-making. Fair distribution of medical resources is considered as an ethical principle. Finally, clinical guidelines are no longer viewed as counter-intuitive, but rather as effective means to reduce the disturbingly high rates of medical error.