Making a diagnosis in practice, developing, practicing and evaluating simple or multiple diagnostic methods and tests as well as making the best rational choices is a continuously evolving domain, covering both already established methods and new technologies. All this may be done for diagnostic methods themselves as well as in the framework of their uses in relation to the treatment, prognosis, effectiveness, efficiency and efficacy of their uses both in prevention and cure. In such a context, is there a pragmatic way to proceed?