In the world of medical and life sciences research, staying up to date on the latest evidence-based research is crucial. Systematic reviews are a powerful tool that can help researchers identify gaps in current research and plan future studies. In this article, we’ll provide a comprehensive guide to conducting a systematic review, including what it is, how to plan and conduct a systematic review, and how to report the results. We’ll also provide several examples to help illustrate the key concepts and steps involved in conducting a systematic review.
What is a Systematic Review?
A systematic review is a scholarly synthesis of existing research on a specific topic, wherein such research is identified through a comprehensive search strategy developed a priori.
Systematic reviews use a comprehensive and systematic approach to identify, evaluate, and synthesize evidence on a specific research question. This approach helps ensure that the review is unbiased and that all relevant studies are included. The end result is a clear and comprehensive summary of the available evidence, which can inform the design and conduct of future studies.
Step 1: Define the Research Question
The first step in conducting a systematic review is to clearly define the research question. This should be a clear and concise statement that specifies the population, intervention, comparator, outcome, and study design (PICOS) of interest. For example, a research question could be “What is the effectiveness of drug A compared to placebo in reducing blood pressure in patients with hypertension?”
Step 2: Develop the Protocol
Once the research question has been defined, the next step is to develop a protocol for the systematic review. This should include a detailed plan for how the review will be conducted, including the search strategy, inclusion and exclusion criteria, and methods for data extraction and analysis. The protocol should also specify the quality criteria that will be used to evaluate the included studies and the methods for assessing the risk of bias.
Step 3: Conduct the Search
The next step is to conduct a comprehensive search of the literature to identify all relevant studies. This should include a search of relevant databases, such as PubMed, Embase, and Cochrane Library, as well as a hand search of relevant journals and conference proceedings. The search strategy should be developed in consultation with a librarian or information specialist to ensure that it is comprehensive and reproducible.
Step 4: Screen the Studies
Once the search has been completed, the next step is to screen the studies to determine whether they meet the inclusion criteria. This typically involves a two-stage process, with an initial screening of titles and abstracts followed by a full-text review of the remaining studies. The inclusion criteria should be clearly defined in the protocol and should specify the PICOS of interest.
Step 5: Extract Data and Assess Quality
Once the studies have been selected, the next step is to extract data from the included studies and assess their quality. This should be done using a standardized data extraction form and quality assessment tool, which should be developed as part of the protocol. The data extraction form should include information on the study design, population, intervention, comparator, outcome, and results, as well as any other relevant information.
Step 6: Synthesize the Results
The final step is to synthesize the results of the included studies. This typically involves a quantitative synthesis, such as a meta-analysis, if the studies are sufficiently homogeneous. If the studies are too heterogeneous, a qualitative synthesis may be more appropriate. The results should be presented in a clear and concise manner, with appropriate measures of effect size and confidence intervals.
Reporting the Results
The results of the systematic review should be reported in a transparent and comprehensive manner. The report should follow relevant reporting guidelines, such as the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement, and should include a description of the methods used, the results of the review, and a discussion of the implications of the findings.
Systematic Review Examples
To help illustrate the key concepts and steps involved in conducting a systematic review, we’ll provide several examples of research questions and how they might be approached using a systematic review.
Example 1: What is the Effectiveness of Drug A Compared to Placebo in Reducing Blood Pressure in Patients with Hypertension?
To answer this research question using a systematic review, the following steps might be taken:
- Define the research question: What is the effectiveness of drug A compared to placebo in reducing blood pressure in patients with hypertension?
- Develop the protocol: The protocol might include a comprehensive search of relevant databases, such as PubMed, Embase, and Cochrane Library, using appropriate search terms. The inclusion criteria might specify that only randomized controlled trials (RCTs) are included and that the population of interest is patients with hypertension who have not previously been treated with drug A. The data extraction form might include information on study design, population, intervention, comparator, outcome, and adverse events, as well as information on the quality of the studies.
- Conduct the search: The search might include a combination of relevant search terms, such as “hypertension,” “drug A,” and “placebo,” as well as appropriate filters to limit the results to RCTs.
- Screen the studies: The studies would be screened based on the inclusion criteria, with an initial screening of titles and abstracts followed by a full-text review of the remaining studies.
- Extract data and assess quality: The data extraction form would be used to extract data from the included studies, including information on the population, intervention, comparator, outcome, and adverse events. The quality of the studies would be assessed using an appropriate tool, such as the Cochrane Risk of Bias tool.
- Synthesize the results: The results of the included studies would be synthesized using appropriate statistical methods, such as a meta-analysis if the studies are sufficiently homogeneous.
Example 2: What is the Effectiveness of Mindfulness-Based Stress Reduction in Reducing Anxiety in Cancer Patients?
To answer this research question using a systematic review, the following steps might be taken:
Define the research question: What is the effectiveness of mindfulness-based stress reduction in reducing anxiety in cancer patients?
Develop the protocol: The protocol might include a comprehensive search of relevant databases, such as PubMed, Embase, and Cochrane Library, using appropriate search terms. The inclusion criteria might specify that only RCTs are included and that the population of interest is cancer patients with symptoms of anxiety. The data extraction form might include information on study design, population, intervention, comparator, outcome, and adverse events, as well as information on the quality of the studies.
Conduct the search: The search might include a combination of relevant search terms, such as “mindfulness-based stress reduction,” “anxiety,” and “cancer,” as well as appropriate filters to limit the results to RCTs.
Screen the studies: The studies would be screened based on the inclusion criteria, with an initial screening of titles and abstracts followed by a full-text review of the remaining studies.
Extract data and assess quality: The data extraction form would be used to extract data from the included studies, including information on the population, intervention, comparator, outcome, and adverse events. The quality of the studies would be assessed using an appropriate tool, such as the Cochrane Risk of Bias tool.
Synthesize the results: The results of the included studies would be synthesized using appropriate statistical methods, such as a meta-analysis if the studies are sufficiently homogeneous.
Example 3: What is the Effectiveness of Different Types of Exercise in Improving Cognitive Function in Older Adults?
To answer this research question using a systematic review, the following steps might be taken:
Define the research question: What is the effectiveness of different types of exercise in improving cognitive function in older adults?
Develop the protocol: The protocol might include a comprehensive search of relevant databases, such as PubMed, Embase, and Cochrane Library, using appropriate search terms. The inclusion criteria might specify that only RCTs are included and that the population of interest is older adults (65 years and older) with cognitive impairment. The data extraction form might include information on study design, population, intervention, comparator, outcome, and adverse events, as well as information on the quality of the studies.
Conduct the search: The search might include a combination of relevant search terms, such as “exercise,” “cognitive function,” and “older adults,” as well as appropriate filters to limit the results to RCTs.
Screen the studies: The studies would be screened based on the inclusion criteria, with an initial screening of titles and abstracts followed by a full-text review of the remaining studies.
Extract data and assess quality: The data extraction form would be used to extract data from the included studies, including information on the population, intervention, comparator, outcome, and adverse events. The quality of the studies would be assessed using an appropriate tool, such as the Cochrane Risk of Bias tool.
Synthesize the results: The results of the included studies would be synthesized using appropriate statistical methods, such as a meta-analysis if the studies are sufficiently homogeneous.
Conclusion
Systematic reviews are a powerful tool that can help medical and life sciences researchers identify gaps in current research and plan future studies. By utilizing a comprehensive and systematic approach for identifying, evaluating, and synthesizing evidence, systematic reviews can help researchers make informed decisions about the design and conduct of future studies. While conducting a systematic review can be a complex process, following the steps outlined in this guide can help ensure that the review is conducted in a rigorous and transparent manner and that the results are reported in a clear and comprehensive way.
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