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Systematic reviews are a critical tool in evidence-based research, enabling scholars and practitioners to gather, assess, and synthesise existing studies on a given topic. Writing a high-quality systematic review can be challenging but is essential for providing a thorough and unbiased summary of research findings. This guide explains the key steps to help you write a comprehensive systematic review that meets academic standards.

What is a Systematic Review?

A systematic review is a type of research article that involves a structured and reproducible process to identify, assess, and synthesise the results of existing studies on a specific research question. Unlike traditional literature reviews, systematic reviews aim to minimise bias and provide a transparent analysis that can be replicated and verified.

Steps to write a Systematic Review

• 1. Define your research question clearly

Start by defining a clear, focused research question that your systematic review will address. This question guides the entire process, ensuring your work remains targeted and relevant. Use the PICO model (Population, Intervention, Comparison, Outcome) to structure your question, which is particularly useful for health and social science reviews. For example:

Population: Who or what is the study’s target audience?
Intervention: What treatment, variable, or condition are you analysing?
Comparison: Is there a control or comparison group?
Outcome: What outcomes or results are being measured?

• 2. Develop a protocol

A systematic review protocol is a detailed plan that outlines your objectives, methods, and inclusion/exclusion criteria. Developing a protocol before starting the review is crucial to ensure transparency and consistency. Register your protocol in an open-access database (e.g., PROSPERO for health research) to enhance credibility and reduce bias by documenting the planned steps before you begin.

Key components of a protocol include:

Research question: Clearly stated and focused.
Eligibility criteria: Define which studies will be included and which will be excluded.
Data sources: List the databases and resources you will search.
Search strategy: Specify search terms, keywords, and Boolean operators.
Study selection process: Explain the screening process to ensure consistency.
Quality assessment: Describe how you will evaluate study quality.

• 3. Conduct a comprehensive literature search

A thorough literature search is the backbone of any systematic review. Search multiple databases to ensure that all relevant studies are included. Major databases include PubMed, Scopus, Embase, and Web of Science, but consider subject-specific databases for specialised topics.

• 4. Screen and select studies

Study selection is a multi-step process that involves:

• Title and abstract screening: Quickly review titles and abstracts to eliminate irrelevant studies.
• Full-Text screening: Review the full texts of shortlisted articles to determine their suitability based on your inclusion and exclusion criteria.

Using systematic review software (such as Rayyan or Covidence) can streamline the process and help manage a large volume of studies. Ensure you apply the same criteria throughout to avoid bias.

• 5. Extract data

Data extraction involves collecting key information from each included study. Create a data extraction form to keep the process standardised. Information to include:

Study details: Author, year, and location.

Population characteristics: Sample size, demographics.

Study design: Type of study, methodology.

Outcomes: Results, statistical measures, and findings.

Systematically extracted data forms the foundation of the synthesis and analysis phase. Use tables to organise and display data.

• 6. Assess the quality of studies

Quality assessment evaluates the risk of bias in each study and helps you determine the reliability of findings. Different tools are available depending on the study type:

• Cochrane Risk of Bias Tool for randomised controlled trials.
• Newcastle-Ottawa Scale for cohort and case-control studies.
• CASP checklists for qualitative studies.

• 7. Synthesise findings

The synthesis of findings can be either qualitative (narrative) or quantitative (meta-analysis). A qualitative synthesis provides a descriptive summary, while a quantitative synthesis statistically combines data from multiple studies to identify trends or pooled effects. In a qualitative synthesis, consider patterns and themes that emerge across studies. For quantitative synthesis (meta-analysis), include effect sizes, confidence intervals, and other statistical measures. Software like RevMan or Comprehensive Meta-Analysis can assist your work.

• 8. Cite your sources

A systematic review relies on rigorous evidence, so include comprehensive citations in a consistent format. This not only strengthens credibility but helps your article rank better by associating it with high-quality sources.