摘要：International medical literature constantly produces a large amount of clinical studies, but only a small percentage of these, when subjected to a systematic critical appraisal, meets the minimum standard of quality. The objective of this paper is therefore to provide the necessary tools for the critical analysis of a study. The three phases of the critical appraisal process are: examination of internal validity (de- tailed analysis of the basic elements composing a trial), relevance of the results (analysis of effect size and accuracy of results), applicability or external validity (comparison of basic elements of a study with the real life setting). The first step is to critically review the fundamental elements of every clinical research: Population, Intervention, Comparison and Outcome. In order to warrant a good methodological quality, with results transferable in the clini- cal practice, the following criteria have to be fulfilled: population representative and described in detail (inclusion and exclusion criteria); interventions (experimental and concomitant) carefully described to make the trial reproducible; outcome as much as possible substantial from a clinical, organizational and beneficial point of view (clinically relevant and/or surrogate endpoints, and their specific characteristics).
