What are systematic reviews?

Pauline Heus, MSc.
Cochrane Netherlands, Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht University, Utrecht

Systematic reviews aim to present an unbiased, comprehensive picture of the available evidence regarding a specific topic, that can be used to support decisions in health care, in policy, or to identify areas where future research may be needed. They use explicit, systematic, and reproducible methods. Key characteristics of a systematic review are:

·         a clearly stated set of objectives, specifying the question to be answered and the type of evidence that will be sought;
·         pre-defined eligibility criteria for studies, that will guide decisions on including or excluding studies for the review;
·         a systematic search that attempts to identify all studies that would meet the eligibility criteria;
·         an assessment of the validity of the findings of the included studies, for example through the assessment of risk of bias; and
·         a systematic presentation, and synthesis, of the characteristics and findings of the included studies.

By these characteristics systematic reviews differ from traditional narrative reviews, for which it is not always clear how the evidence was selected and appraised.
Below, several aspects regarding the conduct and use of systematic reviews will be discussed that, either directly or indirectly, are related to the topic of scientific integrity.