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Systematic Review Guide

In a systematic review, it is essential that two independent reviewers screen each search result in two distinct phases: first by reviewing titles and abstracts, and then by assessing the full-text articles. This dual-review process helps avoid bias and ensures consistency in study selection. When disagreements arise, a conflict resolution step is used to reach consensus, often involving a third reviewer.

The screening process is detailed below.

The planning stage of screening in a systematic review involves preparing and organising how studies will be selected for inclusion. This includes defining clear eligibility criteria, developing and piloting screening tools, setting up screening software or spreadsheets, training reviewers, and agreeing on procedures for resolving disagreements. It ensures the screening process is systematic, transparent, and reproducible.

Why is it important to plan how you screen?

  • Ensures consistency and that all reviewers apply inclusion and exclusion criteria in the same way.
  • Prevents arbitrary or subjective study selection.
  • Improves efficiency – a clear plan streamlines the review process and avoids duplication.
  • Facilitates teamwork by clarifying roles, tools, and processes for reviewers.
  • Helps identify and resolve issues early.

How do I plan the screening stage?

The plans for screening will need to be documented in your protocol. Plans include:

  1. Select a screening tool
    1. Covidence is an easy to use tool available through Monash Health library
  2. Decide who will screen results
    1. At least two reviewers need to screen the results according to the inclusion and exclusion criteria.
  3. Decide if conflicts will be resolved via discussion between the two reviewers or a third reviewer
  4. Decide how to record the results of screening
    1. Use the PRIMSA flow diagram - Covidence can generate one for you.
  5. Test screen a small number of studies (6-10) to ensure all reviewers consistently apply the inclusion and exclusion criteria.

Recommended resources:

Covidence. (2023). PRISMA: download and edit the flow diagram.

The first screening stage involves scanning titles and abstracts of de-duplicated results from all searches. In this stage reviewers will vote on whether to move a result to the next stage (full text screening) or exclude the result because it does not meet the inclusion criteria.

Each result must be independently screened by two reviewers to avoid bias. Conflicts are then resolved by discussion or a third reviewer.

Why is it important to screen the title and abstract?

  • Quickly removes clearly irrelevant papers before full-text review.
  • Reduces the number of full-text articles that need detailed appraisal.
  • Helps maintain alignment with the review’s inclusion and exclusion criteria.

How do I screen the title and abstract?

  1. Add your results to your chosen software tool.
    1. Covidence will automatically remove duplicate results
  2. Scan the title and abstract of each result.
    1. You can add highlights in Covidence to make this stage easier.
  3. Vote to move a result to full text screening or exclude.
    Note: it is best to be over-inclusive at this stage. If you’re not certain, then vote yes to examine the full text in the next stage.
  4. Resolve conflicts according to the plans set out in your review protocol.
  5. Record screening results for your PRISMA diagram if your software does not do this for you.

Recommended resources:

Covidence. (2023). How to screen title and abstract.

The next phase of screening involves checking the full text of each result in this phase to determine whether it meets the inclusion criteria. As with title and abstract screening, two reviewers must work independently to vote on each article. This ensures blinded decision making, reducing bias.

The screeners may resolve conflicts by discussion, or this can be done by a third team member with subject matter expertise.

Why is it important to screen the full-text of studies?

  • Ensures each study truly meets all inclusion and exclusion criteria.
  • Allows reviewers to assess study design, population, outcomes, and methods not evident in the abstract.

How do I screen the full-text?

  1. Source full-text PDFs of all studies
    1. If you're using Covidence, use the LibKey Link to access PDFs
    2. The library can assist with sourcing articles
  2. Examine the full text of each result to check for compliance with the inclusion criteria, assessing eligibility criteria in order of importance.
  3. Vote to include or exclude the result, documenting the reason for an exclusion which should be pre-set by the review team.
  4. Contact study authors if information is missing from the articles (for example, methods or results) before deciding. 
  5. Resolve conflicts
  6. Record screening results for your PRISMA diagram if your software does not do this for you.

Recommended resources:

Covidence. (2023). How to screen by full text.