Advanced literature search and systematic reviews

The final step is to write your methodology to report how you approached your literature search and found appropriate studies. In the methodology you have to clearly document your search process, so that other researchers can reproduce your search and retrieve the same results. 

A methodology must include: 

• The names of the databases you have searched, e.g. Medline, Embase.
• Other sources you have used, for example grey literature such as conference proceedings, theses, official websites. 
• The date you carried out the searches.
• The search limits you applied, e.g. language, date ranges of publication, types of publication.
• Individuals or organisations you contacted.

The search strategies that you applied across the databases (check your search history) can be added as an appendix to the document. This provides additional details on: 

• the search terms you have used.
• the search techniques you applied. 
• how you combined your searches.

The PRISMA Statement

The PRISMA statement is a guideline to help authors improve the reporting of systematic reviews by outlining what needs to be included in a systematic review. The Methods section covers what should be included in your methodology. The statement can be used for other types of research, as well as systematic reviews.

The PRISMA Statement consists of a 27-item checklist and flow diagram. The flow diagram should be completed and added to your review.

Here is an example of a completed PRISMA Flow Diagram.

The purpose of the diagram is to demonstrate the stages you went through to select relevant and eligible research papers, from those you found from your literature search, which you are going to use for your own dissertation/research paper. 

The following numbers outline what should be added in the different boxes in the diagram. Anything which is not relevant to you can be left blank:

1. The total number of results you found from your database searches. If you wish you can note the number of results from each database separately.
2. The number of results which were duplicates.
3. The number of results you were left with once duplicates were removed (the number from box 1 minus the number from box 2). These are the papers which required screening to eliminate those that did not meet your inclusion criteria.
4. The number of results you excluded, after screening their titles and abstracts.
5. The number of results you were left with (the number from box 3 minus the number from box 4)
6. The number of results you could not retrieve e.g. if the full text wasn’t available.
7. The number of results for which you had access to the full text and which required assessing for their eligibility – both for their relevance to your inclusion criteria and their quality (the number from box 5 minus the number from box 6)
8. List the reasons why results were excluded, and the number of results excluded for each reason. (Make a note of the number of results you were left with after exclusion).
9. The number of results you found, separately, from websites; organisations; citation and reference tracking and any other type of resource.
10. The overall total.
11. The number of results you could not retrieve e.g. if the full text wasn’t available.
12. The number of results you were left with which needed to be checked for their eligibility, both for their relevance to your inclusion criteria and quality (the number from box 10 minus the number from box 11)
13. List the reasons why results were excluded, and the number of results excluded for each reason (Make a note of the number of results you were left with after exclusion).
14. Here you need to record the total number of results you are going to include in your dissertation/research paper. (This is the number of results you were left with from box 8 plus those you were left with from box 13).