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.

German Network for Evidence-based medicine. Gute Praxis Gesundheitsinformation. Berlin: 2015.

Institute for Quality and Efficiency in Health Care (IQWiG, Germany). General methods. Version 5.0. Cologne: IQWiG; 2017.

IQWiG health information is written with the aim of helping people understand the advantages and disadvantages of the main treatment options and health care services.

Because IQWiG is a German institute, some of the information provided here is specific to the German health care system. The suitability of any of the described options in an individual case can be determined by talking to a doctor. informedhealth.org can provide support for talks with doctors and other medical professionals, but cannot replace them. We do not offer individual consultations.

Our information is based on the results of good-quality studies. It is written by a team of health care professionals, scientists and editors, and reviewed by external experts. You can find a detailed description of how our health information is produced and updated in our methods.

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Updated on January 16, 2020
Next planned update: 2023

Authors/Publishers:

Institute for Quality and Efficiency in Health Care (IQWiG, Germany)

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