From the life-cycles of clinical evidence to the learning curve of clinical experience.

Treatments on offer to an individual with suspected disease are based on concepts which, like products, go through life-cycles (introduction, growth, maturity, decline). We argue that randomized controlled trials, meta-analyses, and guidelines have reached maturity and/or are already on the decline and note renewed interest in case reports and qualitative medicine. The latter emphasize individual rather than 'average' patients. Moreover, we point out that scientific evidence relates not only to variables that can be measured but also to categorical variables that are often neglected. An appropriate treatment strategy is probably one which is indicated by several methods based on different concepts rather than by a single standard method. The doctor's role is to use his critical judgement and experience to appraise evidence from formal trials and from analyses of observational data and to share his views with the patient.