LibGuides: Covidence: Extracting Data

Introduction to Extraction

See an overview of the extraction phase:

Extraction 2: This is the most current and customizable version and we recommend it for most projects.
Extraction 1: This is designed for Cochrane and similar reviews. It is less flexible than version 2.0.

Setting Up Data Extraction and Quality Assessment Forms

The Data Extraction form must be published before reviewers can begin to extract. The Quality Assessment form is optional.

Covidence offers two sets of template forms (1 and 2), which you can then customize. You can choose which template to use under “Settings” and then “Review Settings.”

You also have the option of building a form from scratch if necessary.

More information:

Data Extraction form
Quality Assessment form (optional)

To facilitated consistent extraction of information, the questions on the forms should:

Be based on what data you intend to report or analyze (e.g., primary and secondary outcomes, sub-analyses, patient subgroups, important definitions)
- Going back later to add information that was omitted is much harder and more time-consuming than planning in advance.
Use as few free text fields as possible to facilitate consistency of data and reduce cleanup on the back end.
Add instructions, where relevant, on how data should be entered (e.g., preferred measure/scale, number of decimal places, formatting of dates and/or percentages, appropriate units).

You can update the forms while extraction is ongoing and the changes will populate to the forms for all studies for extraction, even those already completed.

Pilot testing with a small number of articles will help you refine the forms and reduce the need to edit them later.
If you do make changes, reviewers will need to go back to completed forms to address fields that were added or altered. Even if no changes need to be made, they will need to be submitted as completed again.
If you are doing duel extraction, the revised forms may also need to go through consensus again.

Covidence Data Extraction Guide
This guide provides insights from the global systematic review community, including definitions, practical advice, downloadable templates, and real-world examples.

Conducting Data Extraction and Quality Assessment

See an overview of how to complete the Data Extraction and Quality Assessment forms.

Keep in mind:

If both Data Extraction and Quality Assessment are being conducted, the two forms must be completed by the same reviewer.
- It is possible to have two reviewers enter data into the same extraction form, although it must be done sequentially rather than at the same time. To designate the reviewers and order, use the "Manage reviewers" button under the reference (it will only show up once extraction has started).
Although the “Add full text” button appears in blue below each reference, this does not impact PDFs already uploaded during the full text review. It is there so you can add other full text (e.g., appendices or supplementary materials) if needed.
- You can still get to the original PDF by clicking the “View full text” button.
Comments can be added during extraction to incorporate notes that fall outside the scope of the form itself. They will be visible during the consensus process.
References remain “In Progress” until both reviewers (if applicable) click “Send for Consensus.”

Completing Consensus

See an overview of the consensus process.

Keep in mind:

All extraction forms must go through a consensus phase to determine the final information.
- Even after this process is completed, it is still possible to edit the data if needed.
If two reviewers are used, differences in their responses will show up as conflicts.