First level screening - title and abstract review
At the initial screening stage read just the title and abstract of the candidate studies and make a decision to include or exclude the study from your review.
For small reviews of a few studies (e.g. <100)
The research team should agree on the inclusion and exclusion criteria for studies you wish to review and put together a study screening form. To help identify your inclusion/exclusion criteria, revisit the PICOS of interest you came up with for your search strategy and gain agreement/approval from your colleagues or supervisor. The screening form may look similar to Table 3 of Brown et al (2013). You may write down your decision to include or exclude an article on an Excel spreadsheet like this one, or if you have a small number of records you may choose to print out one copy for each record, although printing will be impractical for larger numbers of records. Screen each potentially useful article identified in the literature search as follows:
For large reviews of many studies (e.g. >100) - in case you need to partially automate the screening process
There are two web-based software applications that can help with screening and tracking your selection decisions:
Second level screening - full text review
Having excluded candidate studies that did not meet your inclusion/exclusion criteria you should have a smaller number of potentially relevant studies. Read and critically appraise the full text of each study you selected at the first pass screening stage to determine whether you wish to include them in your discussion and analysis. Specifically each study must be evaluated based on the following criteria:
Does this study address a clearly focused question?
Did the study use valid methods to address this question?
Are the valid results of this study important?
Are these valid, important results applicable to my patient or population?
If the answer to any of these questions is “no”, you may wish to read no further and exclude the study, or you may decide to include the study to inform your discussion but not include the results in your analysis.
To help with this process you may wish to download and apply one of the example Critical Appraisal Worksheets from the Center for Evidence Based Medicine to each study - choose a worksheet that matches the type of study:
Systematic Review article Critical Appraisal Sheet
Diagnosis study Critical Appraisal Sheet
Prognosis study Critical Appraisal Sheet
Therapy / Randomized Controlled Trial Critical Appraisal Sheet
Make a decision on whether or not to include the study in your review, and write your decision and reasons for inclusion/exclusion at this second level/full text review stage on the study screening form. You will summarise the reasons for exclusion on the PRISMA flow diagram - see Study Selection PRISMA item # 17 below.
Reporting your screening decisions
In the final report in the methods section the PRISMA checklist Item 9 study selection will be reported as:
Researchers must keep the screening forms to create a summary descriptive flow diagram of study selection.
In the final report in the results section the PRISMA checklist Item 17 study selection should be reported as follows: