If you’ve ever tried to look into all the research that’s been conducted on a specific matter, you may have come across a systematic literature review (SLR).
A systematic review of the literature is a type of review that aims to collect and summarize all studies relating to a certain topic in order to answer a research question.
In this article, we will look at the differences between an SRL and a traditional literature review, the key stages of a systematic review, and the key resources and tools for conducting a transparent and reproducible SRL.
Systematic Review of the Literature: What Is It?
A systematic review looks at all existing research pertaining to a specific research question and draws conclusions from it in an unbiased, reproducible, and transparent manner.
Since systematic reviews aim to answer a research question and use rigorous methods to arrive at objective conclusions, they may often require as much focus and academic skill as primary research.
RELATED READ: Credible Scientific Research: Importance of sources
Systematic Review VS Literature Review
The main difference between a systematic review and a traditional literature review is that SLRs strive to minimize bias as much as possible, rely on reproducible and transparent methods, follow key stages, and tend to analyze a narrower yet more extensive scope of research.
What’s more, systematic reviews often involve more than one researcher to reduce bias and clearly state how each reviewed study was identified and evaluated.
Thanks to having these measures in place, systematic reviews make for very comprehensive and transparent pieces of research that are extremely valuable to academics, students, and other professionals in the field.
Since SLRs are very time-consuming and require a great deal of academic skill, a regular bachelor’s or master’s thesis will usually include a typical literature review instead.
How to Conduct a Systematic Review of the Literature: 5 Steps
SLRs follow a set of specific stages to ensure the methodology is reproducible and the results valid.
Starting with…
1) Define your research question
Just as in the case of experiments or other types of studies, a systematic review of the literature aims to answer a particular question.
In order to arrive at your research question, it’s vital that you become closely familiar with all the existing knowledge in the field, analyze it for potential gaps, and start asking questions about the subject matter.
Once you’ve razored in on your question, ask yourself:
- Is it clear?
- Is it focused?
- Is it going to bring something of value to the field?
You can also turn to various search frameworks (acronyms that help you focus your research question better) for help.
For example, here is a search framework that’s often used in medical fields:
- P (patient, population, problem)
- I (intervention)
- C (comparison)
- O (outcome)
There are a few more letters you can add depending on your research and field, such as:
- C (context)
- T (type of study design)
Take clinical trials, for instance.
If researchers are trying to determine whether a specific treatment (I) will work for a particular group of people (P), they may split participants into two groups (C), one of which receives the treatment in question and the other a placebo. The differences analyzed between the two groups and the conclusions drawn from that are the outcome (O).
2) Develop a review protocol
A review protocol is essentially a plan that details how you’re going to go about conducting your systematic review.
This is where you map out your selection criteria, describe which data you will collect and on which grounds you will analyze them, and detail the review process so that it is transparent and reproducible by other researchers.
In a nutshell, your review protocol should ideally include:
- The objectives of your review and your research question
- Selection criteria (why certain studies are included and others excluded)
- Search strategy (how you will look for and choose sources)
- Data analysis strategies (collection of data, managing data, evaluating data)
RELATED READ: Table of contents for research papers
3) Conduct a systematic search
A systematic search requires a search strategy. When looking for your sources, it’s important that you stick to inclusion/exclusion criteria you have defined in your protocol, such as:
- Study design
- Date of publication
- Age
- Geography
- Language
You should also determine which databases you will search based on your field and research question.
For example, PubMed or Cochrane Library are very popular databases in the health sciences.
4) Screen all studies
The next step is to apply selection criteria to all the studies and articles you have found. It is important that you document this process so that you can write it all up later on.
It is generally recommended that there are at least two researchers who screen the studies in question in order to reduce bias.
The screening process is split into two stages:
- Abstracts: Include or exclude studies based on titles and abstracts
- Full texts: Read through the articles that made it through stage 1 and decide whether they meet all the selection criteria
There are many different tools you can use to help with your screening, such as PRISMA or CASP.
5) Extract and synthesize relevant data
Once you have selected all the articles that are to be included in your review, it is time to extract data.
This is to be done methodically, ideally in a table that portrays all relevant data for all studies.
The primary information you are looking for is:
- Each study’s methods and results, including study design, context, sample size, and findings
You should also try to evaluate any potential bias and limitations in the selected studies.
After extraction comes synthesis. This is when you compile all your data into a coherent narrative that paints an objective picture of the topic in question and aims to answer the research question.
Again, you can use various tools and software that make the extraction and synthesis process easier, for example, RevMan or JBI SUMARI.
Conclusion
When all the above-mentioned steps are completed, it is time to write your systematic review (here is a PRISMA checklist that helps you stay on track) and get it published in a peer-reviewed journal or a systematic review database.
And if you need help editing or proofreading your review or other scientific documents, don’t hesitate to reach out to the FirstEditing team.
