Systematic reviews represent a fundamental part of evidence-based healthcare. But why is it called systematic? How does it gain this adjective? In clinical trials a review can be defined as systematic only when it covers several key elements. Precisely, a systematic review is the one that is founded on a clearly structured question, is related to a relevant study, assesses its quality and efficacy, and lastly, offers a summary of empirical evidences accompanied by effective approaches. It is exactly due to the implementation of unambiguous and well-organized methodology that fits pre-defined eligibility criteria that this type of reviews can be distinguished from traditional reviews.
How to perform a successful systematic review?
To do that, there is pre-specified tactic which consists of five guiding steps. They include:
- FORMULATING AN EXPLICIT QUESTION
First things first, the problem which is planned to be reviewed must be addressed in a well-framed question which doesn’t leave space for any misunderstandings or confusion. It should be plainly formed and presented before starting the review process. The question could also be delivered in a free query-like form, but most of the time reviewers prefer it to be set as explicitly as possible. After that, once the question/questions has/have been stated, changes to the protocol can be made only if there are any other ways of determining human subjects, treatments, results or study designs.
- IDENTIFYING APPROPRIATE RESOURCES
There is an extensive and thorough search for current publications/studies involved in the whole review process. In order to capture the most relevant and useful information, one must cover multiple sources and should go over an impressive amount of scientific and medical databases. What is more, the identification of appropriate resources of data and the hunt for applicable references which are directly related to the case being examined also requires accessing tons of web pages scattered around the Internet. Reasons for inclusion or exclusion of any study/publication must be indicated.
- EVALUATING TRIAL QUALITY
After selecting studies of an acceptable design, an in-depth assessment for the risk of different biases should be carried out to guarantee for adequate quality. The estimation of the quality of a study is an on-going process valid through every single step of the review. So such appraising of one intervention or another is expected to offer evidence from a more extensive range of study designs in order to prove that the treatment is safe and will not endanger the life of anyone involved in the research.
- SUMMARIZING THE EVIDENCE
It is essential that investigators collect data from various studies but it is even more essential they sum up these data. This will deliver a well-weighed results/evidences of the primary studies. Such summary will be used as an indicator that shows, for instance, how many of the investigated individuals demonstrated negative associations, how many demonstrated positive associations, how many significant differences were found and so on. The synthesised data can be presented narratively and/or statistically (including numerical and graphical presentations).
- ANALYZING THE FINDINGS
Analysing and interpreting are intuitive processes and cannot be referred to as mechanical. Such scrutiny is focused on figuring out and finding a deeper meaning of what has been found until the present moment. Is the treatment effective? Does it demonstrate high quality levels? Will the use of a drug have negative impact on patients? These are all questions the answers to which lie in the findings and in their interpretation supported by the inspection of their background, content, principles and so on.
In brief, reviewers must make a great variety of decisions when preparing a systematic review. Their careful preparation includes outlining the focus of the review (the question); selecting appropriate resources; assessing the quality of a trial; synthesising evidences and scrutinizing the findings in order to draw the most adequate conclusions.
Finally, in case you want to read more about systematic reviews, you can check our article on the role of these reviews in clinical studies.
