Note: Covidence is making updates and improvements to Extraction 1. If you started extracting data in Extraction 1 before July 4th, 2023, you’ll be using the old version of Extraction 1. You can find support for the old version here.
Start extracting data for a study
Two reviewers and a consensus reviewer must collect data for a study. Any member of the reviewing team can extract data unless you have defined rules in Settings > Team settings.
To begin extracting data, you must first publish a data extraction template. Once a template has been published, click “Start” on a study to begin extraction.
Status of a study
When you are completing extraction for a study, the status is displayed on the study list screen. These are explained below:
- Start - You can start extraction for that study
- Incomplete - You have started extraction but have not completed extraction for that study. Click “Incomplete” to continue extracting data.
- Unavailable - Another reviewer has started extraction. You cannot open extraction for that study. “Unavailable” shows for the consensus reviewer until “Reviewer 1” and “Reviewer 2” has completed data extraction.
- Done - You have completed extraction for that study. If consensus has been reached then you can click on “Done” to see the final data for that study.
The extraction form for a study has multiple sections; summary, identification, methods, population, interventions and outcomes. All fields, characteristics, interventions and outcomes that have been defined on the data extraction template are shown on each study extraction form.
If you want to update the extraction form for a study then you must update the template. We recommend that you speak to the template creator and/or lead reviewer before updating the template as all changes made to the template will be promoted to every study in data extraction. This is so consistent data can be collected across all studies.
When you open the interventions section, you’ll find a list of all interventions that have been defined on the template. The 1st Reviewer can select which interventions were included in the study.
Interventions need to be selected before they appear on the population, interventions and outcome sections.
Once an intervention is selected, a table will appear allowing you to extract intervention details. You can optionally add a group name and add multiple groups per intervention. Adding multiple groups and capturing group names will allow you to accurately report how the intervention or comparator groups have been described in the study.
Only the 1st Reviewer can select interventions, add multiple groups and add group names.
If you deselect an intervention it will be removed from the population, intervention and outcome sections for that study. It will also be removed from exports for that study only. Selecting and deselecting interventions will not impact other studies.
If data has been collected against that intervention on that study and you deselect it, then a warning will appear. You can decide to remove the intervention and all data extracted against the intervention or you can decide to keep the intervention and extracted data.
Only the 1st Reviewer can select interventions and add a group name. If you are the 2nd Reviewer and want to make changes you can check who the 1st Reviewer is on the study list and ask them to make any relevant changes. If needed, you can change the 1st Reviewer by clicking "Manage Reviewers".
When you open the outcome section, you’ll find a list of all outcomes that have been defined on the template. The 1st Reviewer can select which outcomes were included in the study.
Once an outcome is selected, a table will appear with the timepoints you have defined on the template. You can then remove timepoints if they weren’t included in the study. Selecting and deselecting outcomes and timepoints will not impact other studies.
Outcomes need to be selected before they appear on the result section. Only the 1st Reviewer can select outcomes and remove timepoints.
If data has been collected against an outcome or timepoint on the study and you remove it, then a warning will appear. You can decide to remove the outcome or timepoint and all data extracted against it or you can decide to keep the outcome or timepoint and extracted data.
Editing outcome tables
When you first open the outcome section, you’ll find all the outcomes which have been defined on the template with the default measures. If you need to change the measures for an outcome then you can click the edit icon.
Only the 1st Reviewer can edit the outcome. If you are the 2nd Reviewer and want to edit the outcome table you can check who the 1st Reviewer is on the study list and ask them to make any relevant changes. If needed, you can change the 1st Reviewer by clicking "Manage Reviewers".
Different measures will show in the “Reported as” field and you can select to report an effect estimate instead of raw data by changing the “Reported against” field. If you add an effect estimate, you’ll need to select a reference arm before saving the outcome.
When editing the outcome table, you can also collect other outcome characteristics including unit, scale, range, direction of improvement, whether data are a final value or change from baseline, and how complete the outcome reporting is.
Note: outcome characteristics will export to RevMan but not CSV/Excel.
If study data have been reported differently from any of the standard option choices, you can create a custom measure.
Collecting result data
The interventions will appear as rows, and timepoints as columns. These need to be defined on the template, however you can select which ones are included in a study.
If you need to indicate missing data, click the "add 'missing data' tag" button below the table. Missing data cells will appear as grey. To remove this tag, click into the greyed out cells and click "Remove 'missing data' tag".
If you enter data in a format that is different from what is expected, then Covidence will display a red box around that entry. This data will not save or be available at the point of consensus. It will also not export to both CSV/Excel and RevMan.