Evidence Synthesis & Systematic Review Research

Screening is a multi-step process of increasing article/sources scrutiny against the inclusion-exclusion criteria (developed as part of the protocol development prior to the start of this stage). Screening refers to the process of examining individual article/sources decide if they meet the inclusion criteria and will thus be included for further scrutiny or if they contain exclusion elements and will thus be excluded and no longer examined as part of the project. This multi-step process helps deal with starting article collections that are usually quite large (e.g., hundreds or even thousands of articles).

Step 1 - Screen based on title/abstract only: 

• articles are screened in/out against the inclusion/exclusion criteria based on title and abstract information; if the title/abstract is not enough to make an exclusion decision, the article is included at this step
• there is no need to document at the article level why an article is included or excluded at this step; however the total number of articles screened, the number of articles included for further screening, and the number of articles excluded from further screening must be documented

Step 2: Obtain full text

• full text of all articles included after Step 1 is gathered
• if the full text of any article cannot be obtained (e.g., conference abstract; no library holds the full text - which does happen on occasion), and therefore cannot be full-text screened in Step 3, this information must be documented

Step 3: Final screening based on full text

• articles screened in after Stage 1 are then examined at the full-text level and a final inclusion or exclusion decision is made
• inclusion and exclusion decisions need to be documented at this stage for all articles included in the screening
• reasons for excluding any article at this stage must be documented (document what exclusion criteria was met)

The flow diagram graphic allows the reader to understand the processes and decisions made around finding articles and screening articles that result in a final article set for the evidence synthesis project. Careful attention must be given to documenting the results of the (searching and) screening process. Widely accepted guidance for what to document during this stage is included in the PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses) Flow Diagram.

Credit: "PRISMA2020 Flow Diagram" (Evidence Synthesis Hackathon)

Some of the screening tools (e.g.. Covidence, DistillerSR, Rayyan) will generate flow diagrams. Alternately you may generate a flow diagram yourself or use the PRISMA-recommended ShinyApp tool for generating a flow diagram.

What to document will depend on what sources are being searched and if the project is new or is an update to a previously The video below will help clarify why there are four different versions of the 2020 PRISMA Flow diagram.

Screening tools can be simple or complex.

Simple (selected)

• Word or Docs or Pages
• Excel or Sheets or Numbers
• Zotero or EndNote

Complex (selected)

• Abstracker (only supports one level of screening)
• ASReview (ai-aided)
• Covidence
• DistillerSR
• EPPI Reviewer
• Rayyan
• SR-Accelerator
• Sysrev