HOW TO PERFORM A SYSTEMATIC REVIEW

Introduction

In conducting research studies, choosing a particular research study design is necessary to help you achieve your research's aim, objectives, and research question. A systematic review is one of the well-known study designs used in research studies. You may be worried about how to perform a systematic review study; this write-up will guide you on ways you can conduct such a study.

What is a systematic review?

A systematic review refers to collecting other peoples’ published work and studying them to answer your research question in a way quite different from conventional literature review. It involves a systematic approach, i.e. it requires following a scientifically approved guideline for conducting the systematic review. There are five major stages that you must consider in conducting a systematic review that scientific researchers and different institutions generally use. Continue reading to see the steps you need to perform a systematic review.

Stages in a systematic review

The stages include the following: framing the research question, identifying relevant publications, assessing the quality of studies, summarizing the evidence, and interpreting the findings.

• Framing the research question: This is the first stage of a systematic review study. At this stage, you are required to change your research question from free form to a structured format. In most cases, the PICO and SPIDER tools are used in structuring research questions for systematic reviews. The PICO is an abbreviation of Population (P), Intervention (I), Comparison (C), and O (outcome), which are used for quantitative studies. In contrast, the SPIDER represents Sample (S), Phenomenon of Interest (PI), Design (D), Evaluation (E), and Research type (R), which are used for qualitative and mixed-method studies.

The PICO tool is mainly adopted in structuring questions requiring quantitative data, primarily in clinical studies. For example, let us assume that our research question is:

“Is the COVID-19 vaccine safe for children under ten years?” 

Then the structure format of the free form question will be:

1. Population (P) - Children under ten years
2. Intervention (I)- COVID-19 vaccination
3. Comparison (C)- Placebo
4. Outcome (O)- Safety or Adverse effect

The framing of the research question will now enable you to determine your search keywords, such as “COVID-19 vaccination”, “Safety”, “Children under ten years", and "Adverse effects".

In addition, the structured questions enable you to understand the type of studies you will look out for to include in your systematic review. For example, regarding the above question on the COVID-19 vaccine, you need to search for experimental study designs (such as randomized controlled trials).

• Identifying relevant publications

This is the second stage in conducting systematic review studies. At this stage, you need to perform a literature search to identify published relevant articles in scientific databases, which will help answer your structured research question.

Some databases that will provide relevant articles for the above-chosen research topic on the COVID-19 vaccine include Google Scholar, Web of Science, Science direct, and Nursing publications.

You need to use your selected search keywords, introduce Booleans operators and limiters to narrow your search, and identify relevant articles for your systematic review.

For example, AND/ OR are examples of Booleans operators. At the same time, limiters could be a number of years, such as 2015 to 2022, or a particular location. Using the above search keywords, for example, we will have to search for the following “COVID-19 vaccination” AND “Children under ten years”; “COVID-19 vaccination” AND “Children under ten years” AND “Safety”; “COVID-19 vaccination” AND “Children under ten years” AND “Adverse effects”.

It is essential to develop inclusion and exclusion criteria to guide the search for articles. For example, the inclusion criteria: 

1. primary studies on randomized controlled trials
2. Full articles
3. Current studies from 2015 to 2022
4. Papers that are written in English

Exclusion criteria:

1. Studies without full articles or studies whose data could not be extracted
2. Duplicate articles
3. Secondary studies
4. Articles older than 2015

Afterwards, it is essential to use a PRISMA model to select relevant studies to answer the research question and achieve the research aim and objectives.

The PRISMA stands for Preferred Reporting Items for Systematic Reviews and Meta-Analyses. It is an approved model for conducting systematic reviews and is essential for intervention studies.

Figure 1. A PRISMA flow chart

• Assessing the quality of studies

This is the third stage of the systematic review, and you need to assess the quality of the selected studies. You can evaluate the quality based on the research design. For example, following the hierarchical order of research study designs, randomized controlled studies of the experimental study design are known and agreed to be the most quality study designs, followed by analytical designs and finally by descriptive designs in quantitative studies. This stage is essential in removing bias in a research study. You can check for bias by looking at certain factors that may bias the result of the research study, such as the sample size.

• Summarizing the evidence

This is the fourth stage in conducting a systematic review study. You are required to provide a summary of the research studies related to the aims and objective of the studies.

• Interpreting the findings

This is the final stage in performing a systematic review. At this stage, you are to summarize the studies and the results and discuss them in relation to similar published studies as to whether the findings of those studies agree or disagree with your research study.

You also need to interpret the findings based on the outcome of interest established in your studies, such as side effects or adverse effects of COVID-19 vaccination among the children under the age of ten. 

In addition, the interpretation should be critical, i.e. you can provide suggestions or interpretations that brought about the findings of the research study.

It is also essential for you to acknowledge the limitation of the study at this stage. For example, the limitation could result from the time frame for the study, the years of published articles included in the research, and other reasons. 

The bottom line is that if you follow all the steps mentioned above, you will be able to perform a quality systematic review study.