The purpose of hedges are to have a pre-made search strategy to find either a study type or a common medical topic. They can either be validated or non-validated. It's important to note that if you change a validated hedge, it is no longer considered validated.
Do I have to form a question?
It is highly recommended to frame your research in the form of a question. This helps you stay focused in your searching and only gather the information you need to accurately and thoroughly answer the research question.
Creating and searching a question is an iterative and exploratory process. You may have an idea of what you want to research, but it takes some time to determine a precise, searchable question.
After doing a preliminary search of the literature and honing your interests, you can then form a specific, searchable question.
Framing your search in the form of a precise question allows you to clarify the criteria needed for selecting relevant studies. An example question for research might be: Have laws limiting soda sales decreased rates of obesity in children?
In clinical medicine, one technique for creating a searchable question is to put it in the form of a PICO question.
We could form a PICO from our previous question about childhood obesity and soda laws:
Not all questions are comparing two treatments or interventions, so it is possible to follow a PICO and not include a comparison.
Once you execute a search, it may be that you do not find anything that answers your question. This can lead to either thinking of new or more terms to represent your PICO elements, or reframing your search question entirely. Research -whether bench, clinical or literature - is an iterative process.
PICO may not specifically apply to your research question, but the principle of breaking your question into searchable chunks still applies.
Different databases require different search strategies. Some have controlled vocabularies, while others are keyword-based; but all databases are more easily searched if you think of the terms that represent each idea in yourquestion prior to searching.
In a systematic review, you are required to search databases that use both controlled vocabularies and keywords. Setting up a simple chart like the pone below can help you stay organized in your searching. Create a column to represent each idea and two rows beneath. One row is to generate the controlled vocabulary terms that describe the topic, while the other are all of the synonyms and phrases to express the idea in a keyword search. terms within a column will typically be combined with OR, while different columns will be combined with AND.
Multiple charts might be made throughout a Systematic Review; perhaps one for each database searched, or a new iteration if terms were added or removed from a different iteration of the search later in the study.
It is important to keep track of your searches and results every step of the way in a Systematic Review. If you've read the PRISMA Guidelines, you know that there is a flow chart that should be included with your review which maps the results found, excludes vs. includes, reasons for decisions and dates. A spreadsheet in Excel can help you keep track of your searching workflow. Columns include:
It is important to keep in mind that the length of time required to do a Systematic Review means you will likely have to rerun searches you did a year ago in order to update any information that may have been recently published.
Many databases allow you to create personal user accounts and save searches in order to run updates later.
Two popular services are MyNCBI for PubMed and personal accounts in Web of Knowledge.
If you do not have a MyNCBI account, it is free to register. Simply go to PubMed, click on the "Sign in to NCBI" link in the upper right hand corner of the page and follow the instructions for registration.
If you are searching PubMed while signed into your MyNCBI account, you have the option to save a search and send email updates to yourself. You can also skip the email updates and just save the search in order to run it at a later time of your choosing.
Watch a brief video tutorial HERE.
NLM/NIH provides a guide to using MyNCBI HERE.
ISI Web of Knowledge
Similar to MyNCBI, by going into Web of KNowledge and registering for an individual account, you can save searches and have email alerts sent you if you choose.
UC Berkeley Library has a brief how-to HERE.