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HMSOM Medical Elective: Developing Search Skills

What is PRISMA?

PRISMA stands for Preferred Reporting Items for Systematic Reviews and Meta-Analyses.

It is an evidence-based minimum set of items for reporting in systematic reviews and meta-analyses.

The aim of the PRISMA Statement is to help authors improve the reporting of systematic reviews and meta-analyses.  PRISMA can be used as a basis for reporting systematic reviews, randomized control trials or other types of research. The PRISMA flow chart describes evidence-backed details in a transparent manner so that users can easily and fully understand how the research was done.

There are two main components of PRISMA:

  1. A checklist of items and a flow diagram. The 27-item checklist includes title, summary, method, results, discussion, and cost of future studies. The four-phase flow diagram provides the final meta-analysis based on the reporting standards. 
  2. The four phase flow diagram depicts the flow of information through the different phases of a systematic review. It maps out the number of records identified, included and excluded, and the reasons for exclusions.

"The PRISMA Explanation and Elaboration document explains and illustrates the principles underlying the PRISMA Statement. It is strongly recommended that it be used in conjunction with the PRISMA Statement.


The PRISMA flow diagram or flow chart is typically the first figure in the results section of your systematic review or many other type of research designA PRISMA flow diagram visually depicts the authors’ process of finding published data on the topic and how they decided whether to include it in the review.

From a PRISMA diagram, the reader can quickly and easily see:

  • how many studies the review screened
  • how many were included
  • what exclusion criteria were used

Although writing a narrative literature review is not as comprehensive as a systematic review would be, it will give you the chance to use the PRISMA flow chart process on a smaller scale. You will search for articles, grey literature and then document how you exclude articles from your final selection. The general process looks something like this:

  1. Search for articles, and then remove any duplicates.
  2. Looking at the articles titles and abstracts, exclude articles based on your screening criteria (you decide what this criteria is).
  3. Retrieve the full text of your remaining records. If you are unable to get the full-text of any articles, you would document this.
  4. Read your remaining full-text articles, and then run them through your exclusionary criteria again. 

The PRISMA flowchart below is for Databases, Registers, and Grey Literature because it has an additional column on the right side of the diagram for reporting of grey literature searches and results.

Explanation of Terms Used on PRISMA Diagram

Step by Step Use of the PRISMA Flow Chart

Step 1: Preparation To complete the the PRISMA diagram, save a copy of the diagram to use alongside your searches. It can be downloaded from the PRISMA website or the box above.

These are the Steps to completing the LEFT Side of the PRISMA flowchart on Database Searching.

Step 2: Doing the Database Search: Run the search for each database individually, including ALL your search terms, any MeSH or other subject headings, or truncation. Apply all your limits (such as years of search, English language only, and so on).

Once all search terms have been combined and you have applied all relevant limits, you should have a final number of records or articles for each database.

Enter this information in the top left box of the PRISMA flow chart. You should add the total number of combined results from all databases (including duplicates) after the equal sign where it says Databases (n=). Many researchers also add notations in the box for the number of results from each database search, for example, Pubmed (n=335), Embase (n= 600), and so on. 

If you search trial registers, such as ClinicalTrials.govCENTRALICTRP, or others, you should enter that number after the equal sign in Registers (n=).

Step 3: Remove All Duplicates: To avoid reviewing duplicate articles, you need to remove any articles that appear more than once in your results. You may want to export the entire list of articles from each database to a citation manager such as Zotero, (including both citation and abstract in your file) and remove the duplicates there. 

Enter the number of records removed as duplicates in the second box on your PRISMA flowchart.  If you are using automation tools to help evaluate the relevance of citations in your results, you would also enter that number here.

Step 4: Records Screened- Title/Abstract Screening: The next step is to add the number of articles that you will screen. This should be the number of records identified minus the number from the duplicates removed box.

Step 5: Records Excluded- Title/Abstract Screening: You will need to screen the titles and abstracts for articles which are relevant to your research question. Any articles that appear to help you provide an answer to your research question should be included. Record the number of articles excluded through title/abstract screening in the box to the right titled "Records excluded."  You can optionally add exclusion reasons at this level, but they are not required until full text screening.

Step 6: Reports Sought for Retrieval: This is the number of articles you obtain in preparation for full text screening.  Subtract the number of excluded records (Step 5) from the total number screened (Step 4) and this will be your number sought for retrieval.

Step 7: Reports Not Retrieved: List the number of articles for which you are unable to find the full text.  Remember to use LibKey Nomad to get full text of your materials and Interlibrary Loan to request articles to see if we can order them from other libraries before automatically excluding them.

Step 8: Reports Assessed for Eligibility- Full Text Screening:  This should be the number of reports sought for retrieval (Step 6) minus the number of reports not retrieved (Step 7). Review the full text for these articles to assess their eligibility for inclusion in your systematic review. 

Step 9: Reports Excluded: After reviewing all articles in the full-text screening stage for eligibility, enter the total number of articles you exclude in the box titled "Reports excluded," and then list your reasons for excluding the articles as well as the number of records excluded for each reason.  Examples include wrong setting, wrong patient population, wrong intervention, wrong dosage, etc.  You should only count an excluded article once in your list even if if meets multiple exclusion criteria.

Step 10: Included Studies: The final step is to subtract the number of records excluded during the eligibility review of full-texts (Step 9) from the total number of articles reviewed for eligibility (Step 8). Enter this number in the box labeled "Studies included in review," combining numbers with your grey literature search results in this box if needed.  You have now completed your PRISMA flow diagram, unless you have also performed searches in non-database sources.

That is how you complete the LEFT SIDE the PRISMA flow chart for database searching results! 

Now you want to complete the RIGHT SIDE of the PRISMA flowchart for your Grey Literature searching results!

If you have searched additional sources, Grey Literature, including such as professional organization websites, government sites, or cited or citing references, etc., complete the RIGHT SIDE of the PRISMA flowchart for that information.


PRISMA Flowchart Downloads