[Evidence-based pharmacy--assessment of study quality].

After having identified relevant studies through a literature search for a specific question, it is now necessary to consider the trustworthiness of the publications found. This article deals with the quality assessment of the raw material "information". The focus is based on the following questions: (a) Why is the randomized controlled trial (RCT) the gold standard for proving a cause-effect relationship? (b) What types of biases exist? To identify the risk of bias, it is necessary to become familiar with some terms. The aim of the current paper is to clarify and explain the key points for the assessment of internal validity of RCTs. The underlying question is: Can I trust the results of this study at all? And: Is it worthwhile to read further? In addition, an example of how to structure a "critical appraisal" will be shown. For this purpose, checklists are helpful to systematize and document the procedure.