8. Data extraction
Data extraction implies the process of extracting the information from the selected studies that will be ultimately reported. In order to allow an efficient data extraction, the process should be detailed in the protocol before the literature search is started. Key components of the data extraction include:
- information about study reference(s) and author(s);
- verification of study eligibility;
- study characteristics:
- study methods
- participants
- interventions
- outcomes measures and results
Evidence tables
All validated studies identified from the systematic literature review relating to each key search question are summarized into evidence tables. The content of the evidence tables is determined by the entire project group. Completion for all retained articles is done by one member of the project group and checked by another member. A KCE template for evidence tables was developed using the CoCanCPG evidence tables (www.cocancpg.eu/) and the GIN evidence tables (http://g-i-n.net/activities/etwg/progresses-of-the-etwg) as a basis, and can be found in attachment. A template is available for systematic reviews, intervention studies, diagnostic accuracy studies and prognostic studies.
GRADE evidence profiles
To provide an overview of the body of evidence for each comparison relevant to the research question, GRADE evidence profiles are created and added to the appendix of the report. These evidence profiles can serve as a basis for the content discussions during the expert meetings. To create these evidence profiles it is highly recommended to use the GRADEpro software, which can be downloaded for free (http://ims.cochrane.org/revman/other-resources/gradepro/download).
When a meta-analysis is possible, it is recommended to extract the necessary information to Review Manager (RevMan) first, and subsequently to import this information from RevMan into GRADEpro (using the button ‘Import from RevMan’). More information on the use of RevMan can be found here: http://ims.cochrane.org/revman.
Once all information is extracted in GRADEpro, evidence profiles can be created by clicking the ‘Preview SoF table’ button, selecting the format ‘GRADE evidence profile’ and exporting them to a Word Document.