Systematic Review | Definition, Steps & Comparison With Other Reviews

As a research scholar or professional of any academics, it is necessary to stay up to date with the relevant research in your field. However, with so many papers available, it can be quite difficult to assess their quality and accuracy.

Systematic reviews are reviews of already existing research, that help to answer research questions and carefully analyse and evaluate the evidence that exists. These reviews entail a statement called protocol in academic research, which provides a detailed explanation of the application and methodologies to be used.

What Is A Systematic Review?

Systematic reviews are a comprehensive analysis of existing research that is carried out to get a reliable and detailed assessment of the research at hand. It aims to reduce bias by evaluating and synthesising information about the specific topic.

Systematic literature reviews are carried out by health professionals and medical researchers but can be found in other academic fields and disciplines as well. Also, it is necessary to familiarise yourself with the whole process as writing a systematic review requires quality research and coherence in structure.

Why Is It Important To Be Systematic?

Systematic reviews differ from other traditional literature reviews and have gained popularity over the last few years. Literature reviews simply introduce a topic, provide information and give some examples for understanding. However, systematic reviews are important in research methods as they provide transparency in how conclusions are made in research. They avoid misrepresentation and provide detailed and logical knowledge of how the research was carried out, and evaluated for findings and data.

Characteristics Of A Systematic Review

Some popular features or characteristics of systematic reviews are:

• Pre-defined eligibility criteria with clearly set objectives
• They combine both qualitative and quantitative approaches for reviews.
• Data extraction and synthesis from each study for sound research.
• Assessing the validity of findings by checking for bias.
• Established guidelines for conducting reviews such as PRISMA, ENTREQ and RAMESES.
• Standardised and reproducible methodologies.

Steps On How To Write A Systematic Review

Before writing a systematic review, it is crucial to check if any other sources provide similar systematic reviews on the topic you have chosen. Change the research question in case you find an already existing review on the specific topic. Here’s how you can write a step-by-step systematic review:

Step 1: Formulate Research Problem

Forming the research question is the most important step in the process of a systematic review. A good research question in a systematic review consists of four components, that you can remember by the acronym PICO; which stands for Populations, Interventions, Comparisons, and Outcomes.

Step 2: Protocol For Systematic Review

Establishing the protocol is the second most crucial step in a systematic review. It includes background information on the research problem, objectives and rationale of the research and the research methodologies to be applied.

Step 3: Finding All Relevant Sources

Find all relevant sources that can assist you in the systematic review. This includes going through journals and other literature reviews and searching multiple databases on the internet. Additionally, going through grey literature such as white appears, government documents and statistical reports are also helpful for systematic reviews.

Step 4: Selection Criteria And Data Extraction In Systematic Review

Apply for the selection criteria, and extract the study’s data. This includes study design, sample size, context, research findings and conclusions. If you are unable to find the relevant data, you will have to contact the study’s authors.

Step 5: Synthesise All Data

Synthesise all the data, which means structuring the data in a coherent manner. You can use both narrative and quantitative approaches to structure the data.

Step 6: Write The Review And Publish It

The last step of a systematic review is writing and publishing it. Your work should consist of the following components;

• Abstract: A summary of the systematic review
• Introduction: Including the research problem, aims and objectives. It can also include the rationale behind choosing this research problem.
• Methods: This part must include the data extraction method, selection criteria, and search methods.
• Results: This shall include results of the selection process, study characteristics, risk of bias and synthesis results.
• Discussion: This part includes the interpretation of results and limitations of research.
• Conclusion: The answer to your question and future tips for research.

Systematic Review Vs Meta-Analysis

A systematic review is a comprehensive analysis of existing research, whereas a meta-analysis is a statistical analysis or combination of results from two separate studies. Here’s how the two differ from each other:

Characteristics	Meta-Analysis	Systematic Reviews
Scope	It mostly focuses on the quantitative results of multiple studies for statistical analysis.	It includes qualitative, quantitative and mixed research methods for various studies.
Synthesis	It follows a quantitative approach, with similar studies and outcomes.	It follows a narrative (qualitative) synthesis of findings.
Heterogeneity	Can not handle heterogeneity, as it can affect the validity of results.	Can handle heterogeneity where studies can be from different populations, designs and interventions.

Literature Review Vs Systematic Review

A traditional literature review uses a less systematic and formal approach to writing a review of research. It may be less challenging and time-consuming than a systematic review, but unfortunately, it has a higher risk of bias. The following are some stages that differ in both these reviews:

Elements	Literature Review	Systematic Review
Question	The research areas or questions are broad, with multiple areas of focus.	It starts with a precise research problem. All the data is collected to just answer that one question.
Searching	Data searching is carried out but not necessarily in any order. It also lacks comprehensiveness.	A rigorous and detailed search is carried out, with certain protocols and methods.
Selection	There may not always be a clear rationale as to why a specific study was included or excluded.	Clear reasons and rationale are produced and informed as to what was included and excluded for the systematic review.
Assessment	Individual reports and studies are not assessed for quality or objectivity.	Each study is assessed for accuracy, objectivity and transparency.
Protocol	No protocols or specific strategies are included.	Certain protocols and peer-review planning are carried out.

Scoping Review Vs Systematic Review

Here is how scoping review differs from systematic review:

Feature	Scoping Review	Systematic Review
Methodology	Less structured, and more exploratory into broad topics	Follows rigorous and structured methodologies.
Purpose	Examine key concepts and knowledge gaps of a particular research topic	Provides answers to a particular research question of existing research.
Criteria	Criteria for inclusion/exclusion can be developed at any stage.	Criteria for inclusion/exclusion are defined beforehand.
Synthesis	Provides a descriptive overview of the literature and does not necessarily use quantitative synthesis.	Uses quantitative and meta-analyses for synthesis.
Question	The research topic in the scope review addresses a broad question or area.	The research question consists of narrow parameters.