[Evidence and medical decision-making--what kind of evidence do we really need?].

The principle of evidence-based medicine and its associated hierarchy of study designs has been the topic of numerous, and sometimes controversial, discussions. We are convinced that the current evidence hierarchy based upon study design is not suitable for all situations in medical decision-making, for example those related to the reality of care. We would like to show that, for a number of medically important questions (e.g. in policy-making), study designs other than RCTs are required, and would therefore propose that evidence levels be based on an objective evaluation of the quality of the study (free of bias, confounding or effect-modifiers) rather than of the specific design.