Average time (hours) to complete | |||||||
88 |
In Step 7, you will skim the full text of included articles to collect information about the studies in a table format (extract data), to summarize the studies and make them easier to compare. You will:
For accuracy, two or more people should extract data from each study. This process can be done by hand or by using a computer program.
If you reach the data extraction step and choose to exclude articles for any reason, update the number of included and excluded studies in your PRISMA flow diagram.
A librarian can advise you on data extraction and charting for your review, including:
In this step of the systematic or scoping review, you will develop your evidence tables, which give detailed information for each study (perhaps using a PICO or PCC framework as a guide), and summary tables, which give a high-level overview of the findings of your review. You can create evidence and summary tables to describe study characteristics, results, or both. These tables will help you determine which studies, if any, are eligible for quantitative synthesis.
Data extraction (charting) requires a lot of planning. We will review some of the tools you can use for data extraction (charting), and the types of information you will want to extract
How many people should extract data?
The Cochrane Handbook and other studies strongly suggest at least two reviewers and extractors to reduce the number of errors. The librarian usually does not help with the data extraction but may assist in preparing for the data extraction such as creating spreadsheets, etc.
There are benefits and limitations to each method of data extraction. You will want to consider:
For example, in Covidence you may spend more time building your data extraction form, but save time later in the extraction process as Covidence can automatically highlight discrepancies for review and resolution between different extractors. Excel may require less time investment to create an extraction form, but it may take longer for you to match and compare data between extractors. More in-depth comparison of the benefits and limitations of each extraction tool can be found in the table below.
Tool | Benefits | Limitations |
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Review Software (Covidence) |
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Spreadsheets (Excel, Google Sheets) |
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Cochrane Revman |
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Survey or Form Software (Poll Everywhere, Qualtrics, etc.) |
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Electronic documents (Word, Google Docs) |
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In a recent article by Pollock et al (2023), a recommendation of what items should be collected in the data extraction phase. They recommend creating 2 tables; the first table includes basic information about the article (which they call the Guidance sheet) and then the 2nd table includes more detailed information.
Other templates:
JBI's recommended scoping review data extraction instrument for study details, characteristics and results extraction.
An example data extraction table from the PRISMA-ScR.
Your protocol should include a plan for how you will present your results.
Your PCC inclusion criteria will assist you in choosing how the data should be mapped most appropriately, but you can refine this toward the end of the review, when you have a better picture of the sort of data available in your included studies.
The results of a scoping review may be presented in your final paper in a variety of ways, including:
The latest guidance (Pollock et al. 2023) encourages 'creative approaches...to convey results to the reader in an understandable way' such as word clouds, honeycombs, heat maps, tree graphs, iconography, waffle charts and interactive resources.
Note: If you present your data in a table/chart, also include a narrative summary to explain how the results relate to your review objectives and questions.
Pollock et al. 2023, JBI Evidence Synthesis, 21(3): 520–532.
JBI advise (11.3.8.1 Search results) results can be classified under main conceptual categories, such as:
'For each category reported, a clear explanation should be provided.'
Joanna Briggs Institute also has a template for data collection and extraction for systematic reviews in section 12.2.9.
Cochrane Manual Handbook for Systematic Reviews includes a chapter on data collection and extraction in section 5-3.
You should plan to extract data that is relevant to answering the question posed in your systematic review.
It may help to consult other similar systematic reviews to identify what data to collect or to think about your question in a framework such as PICO.
Helpful data for an intervention question may include:
If you plan to synthesize data, you will want to collect additional information such as sample sizes, effect sizes, dependent variables, reliability measures, pre-test data, post-test data, follow-up data, and statistical tests used.
Extraction templates and approaches should be determined by the needs of the specific review. For example, if you are extracting qualitative data, you will want to extract data such as theoretical framework, data collection method, or role of the researcher and their potential bias.