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Systematic Reviews

Searching

A preliminary search is about planning and developing your protocol. It helps the research team understand what the review would/should entail, and the preliminary search will also give an estimate for the time and funding commitment necessary for the investigation. Researchers should assume an exhaustive search will identify about 2-3 times more the number of citations than the preliminary search. 

1. Searching for research trends 

  • You need to see a sample of the research trends within the research area. You don’t know the general scope of the literature until you run a preliminary search. You must also sample these results for information for the background and objectives' section in the protocol. Check out the TMC Library's Search Tutorials.

  • A sampling of the preliminary results also helps you formulate The Research Question. The research question must be shaped by the pre-existing literature because enough pre-existing literature must exist in the first place to attempt to answer the research question.

2. Look to see if a systematic or scoping review already exists

  • Look to see if someone has already published a systematic/scoping review on your topic. This is again to analyze the research trends, but it is also important to not duplicate work that is already done.

3. Determine if a Systematic Review is Warranted

  • After you have done a preliminary search to determine research trends and looked to see if a a systematic or scoping review already exists on the topic, you must determine whether a systematic review is warranted. You may also determine that another review type is better for the research topic/question. 
  • Check out the resources to determine whether a systematic review is warranted:

4. Identifying preliminary MeSH/Subject Headings and keywords/keyphrases

  • You can identify the preliminary MeSH/subject headings, keywords, and key phrases you will need. You will have more terms in your final search, but you must identify the basic subject headings and keywords you will need. This is the information that goes in your Search Methods section of your protocol. What goes in this Search Methods section of the protocol are the terms you found during your preliminary searching phase.

  • For those who have been accepted for the Full Service, in the protocols you submit with your application; we ask that you identify the basic keywords for the search in the protocol. What is most helpful is if you provide the search terms you used to access relevant articles on the topic in the protocol. If acronyms are listed, please spell out and define. 

5. Getting test articles

  • Select 5-10 test articles from the preliminary search to use to test your future, exhaustive search strategy (i.e. the search to get your citations for your review). These 5-10 test articles should be articles that *should* make it to the end of review based on inclusion/exclusion criteria. 
  • Researchers may have access to journal subscriptions. Being familiar with a journal and finding articles on the team's topic helps to see what research exists. It can help the information specialist find relevant subject headings and keywords for the search strategy. Additionally, the search strategy that is developed should be able to retrieve these articles that are known to directly address the team's research question.

6. Preparatory contacting of experts

  • One of the goals of contacting experts is to identify unregistered studies with unpublished results. It is important to find experts on the research question because they will know what the current climate is on the research topic. Finally, the research team could benefit from this networking for later stages in the review. 

The Exhaustive Search 

For those utilizing the Basic Service, we recommend the following resources to assist you with developing the exhaustive search to translate to the other predefined databases and to get the citations. 

For advanced search assistance check out the more advanced resources below:

If your application has been approved for the Full Service, the liaison librarian will develop the exhaustive search strategy. However, researchers are encouraged to check out the searching resources for other projects they may have. 

Hand Search / Citation Search

Hand searching can help identify grey literature like conference proceedings, abstracts for posters, and presented papers. Hand searching is usually grouped with "citation searching," or using a citation to find other citations. This is related to the snowball method, and databases like Web of Science can assist with this. A different PRISMA diagram, PRISMA + Other sources, must be used if you include hand search results or citation search results. 

Sources to hand search include:

  • subject specific professional association websites; 
  • included studies' bibliographies;
  • topic review bibliographies.

Hand searching can be done within research centers such as archives that house information resources out of circulation. It is important to document all sources searched by hand. Information regarding the number of hand searched resources used and where resources are located should be reported within the PRISMA Flow Diagram.

1. Clarification of the data

Some systematic reviews involve a meta-analysis. There may be questions regarding the data produced from the study. Contacting experts to clarify data findings helps develop better accuracy and transparency of the information that will be generated from the systematic review.

2. Images

There are some systematic reviews, which require image analysis. Images that are used within published journals may not be easily synthesized or examined. The quality of the original image published in the journal article could make analysis difficult. Contacting the researchers for the raw data images will help the systematic review team better conduct image synthetization and analysis. 

3. New developments 

A systematic review can take 1-2 years. After the search strategy is developed the search has to be deduplicated. When a search is reran, some new articles may be retrieved. Being in contact with the experts helps the systematic review team know what other research is out there, so that information can be put into the review for the principle of transparency. 

Additional Search Tools

Searching for Clinical Trials

Cochrane advocates the use of the Cochrane Central Register of Controlled Trials (CENTRAL). However, there are additional resources for locating randomized controlled trials. Take a look at other clinical trial databases to determine if there might be additional data that could affect the results of your systematic review.