This article covers the key differences between Extraction 1 and Extraction 2.


Summary comparison

The features of Extraction 1 and Extraction 2 are compared in the following table:


Extraction 1

Extraction 1 is designed specifically for intervention reviews. It includes specific sections which allows you to collect data for interventions and outcomes. You can add custom fields if you wish to collect more data. We recommend it for Cochrane reviews because it has an export pathway to Review Manager (RevMan). New data extraction and quality assessment templates are now available in Extraction 1. 

To begin extracting data, you must first publish a data extraction template

To use the quality assessment template, you need to create a quality assessment template. Once the templates have been published, click “Start” on a study to begin extraction. 



Extraction 2

Extraction 2 is more flexible in terms of the types of data you can collect. It is fully customisable and includes single choice fields, multiple choices, and tables. However, it doesn't include specific sections for interventions and outcomes and data do not export to RevMan. It's more suited for all other projects, including scoping reviews and qualitative reviews. 

To begin extracting data, you must first publish a data extraction template

To use the quality assessment template, you need to create a quality assessment template to get started. Once the templates have been published, click “Begin extraction” on a study. 


Updating the template

In Extraction 1 changes to the template will now be applied to all studies to ensure consistent data collection across studies. In Extraction 2 changes to the template also apply to every study. 

Extraction and consensus

In Extraction 1, the process has two stages: 

  1. Extraction itself, which must be performed by two reviewers working independently of each other to produce their own set of data, and 

  2. The consensus stage: one person reviews the two sets of extracted data and decides on the final dataset. the consensus data will be exported.

Extraction 2 has a similar two-stage process consisting of extraction and consensus but, unlike Extraction 1, it also supports a single reviewer extraction process. In single-reviewer data extraction the second stage is a simple check, rather than a comparison, of the data. This check can be done by any member of the team.

Re-assigning reviewers

If a reviewer has started data extraction or consensus you can re-assign the study to another member of your review team by using the 'Manage reviewers' function beneath each study. This feature is available in Extraction 1 and Extraction 2.

View history

In Extraction 1, it is possible to view the previous actions taken on a study by selecting the 'History' button. This is not yet available in Extraction 2.

Un-merge studies

It is now possible to un-merge studies in both Extraction 1 and Extraction 2. 


In Extraction 1, it is possible to export your data to csv, xls, RevMan 5, RevMan Web. You can export your data to csv only in Extraction 2. 

Switching between the tools

You can switch between the two versions of extraction in Settings. This can be useful as a workaround if the tool you are working in does not allow you to view history for example. When you switch to the other tool, all the data in the current tool will be saved. It is not possible, however, to transfer data from one tool to the other.

Demo review

When you are logged in to Covidence you can try out both versions of extraction in our demo review and decide which one best suits your needs. Just go to the ‘Your reviews’ page and scroll to the bottom to see this option. The demo review is pre-populated with some test data and resets regularly.