Evidence-based medicine

Evaluating the evidence

Not every study that is published provides reliable results so it's important to critically evaluate every study. This is a central part of every systematic review. If you do a search for studies in a particular area, you'll often find hundreds or even thousands of hits. If you then take a closer look at the quality of those studies, it often becomes clear that only a few of them can really provide reliable answers.

In “good” systematic reviews, the authors describe in detail what they looked for, how they looked for it and how they analyzed their results. For this reason, we only use reviews that meet these and other minimum requirements, and that only have minor methodological flaws.

We assess the quality of reviews using a checklist known as the Oxman and Guyatt index. This index looks at, for instance, whether the reviewers’ search was extensive enough, and whether the studies they included were evaluated properly.

If we find several systematic reviews of suitable quality, we take a closer look at the individual results in order to identify the best reviews.

We assess qualitative studies based on whether we can follow how they were carried out and whether they adequately addressed the issue in question.