Your search must be both comprehensive and replicable. In the appendix of your publication you should include a search strategy with sufficient detail that that it can be re-run reliably.
The first step is having a clearly defined question. Your PICO(S) should guide your choice of search concepts. Before you start, it is help to do some brainstorming of the various terms used to describe your topic.
Before starting your search, ask yourself what are the key concepts of your question?
In people who ride bicycles (P), are helmets (I) effective in preventing head injury (O)?
The major concepts are: bicycles, helmets, head injury. What are all the words that describe these concepts?
Example: Keyword search in Ovid Medline
Another way to find synonyms is to check the "Used For" or "Entry Terms" in a database that uses subject headings. These can be seen when you check the subject heading description.
Subject headings are pre-defined "controlled vocabulary" words used to describe the content of each item. Subject headings are selected by indexers from a list and assigned to an article to make searching easier. Each database uses its own subject headings - Medline's are called MeSH (Medical Subject Headings).
|Keywords||MeSH Subject Heading|
When you use the subject heading you will capture articles about older people without having to search on all the many other words.
Boolean operators connect your search terms together to either narrow or broaden your set of results. The three basic Boolean operators are: AND, OR, and NOT. Boolean operators must often be capitalized.
With longer sets of terms you will need to combine them using parentheses just like in math problems.
E.g. (cyclists OR bicycles) AND (helmets OR “head protection”)
You can use truncation to expand your search and save time. In most databases this done by using an asterisk* at the end of the root word.
For example, child* will find results with the words:
Wildcards substitute a symbol (often a question mark) for one letter of a word. This is useful if a word is spelled in different ways, but still has the same meaning.
E.g. colo?r will find color, colour
A phrase search looks for two or more words as an exact phrase. Databases usually require phrases to be placed within double quotes, for example, “critical care”. Without the double quotes, the database will search for the words individually anywhere in the record (i.e. as critical AND care).
Almost all databases allow you to search specific fields in the bibliographic record such as title, abstract, author, journal title. Searching specific fields such as title and abstract only can allow you to do a more focused search. Check the Advanced Search options if field searching is not available in the basic search.
Also known as forward and backward citation searching or “snowball” searching, you can check for articles listed in the bibliographies of key articles to see if there are additional relevant studies. You can use Web of Science, Scopus, Web of Science or Google Scholar to link to the articles that have cited key articles.
Once you have created a search strategy, save it within the database so that you can re-run it later or set up alerts to email yourself new results on a regular schedule. You can do this by registering for a personal account within the respective database.
Keep the search history records so that you can document your work later.
The Canadian Agency for Drugs and Technologies in Health (CADTH) Peer Review Checklist for Search Strategies (PRESS) is a checklist of items to aid in the assessment of electronic database search strategies. This checklist is recommended for use by librarians undertaking the peer review of systematic review search strategies.
It is important to continuously monitor the literature for new studies on your topic. Once you have created a search strategy and saved it your personal account within the database, you can use it to run automatic updates or alerts to be sent to your email.
You can also set up table of contents alerts from specific journals.
Each database had a slightly different method for created accounts and alerts. See for example, the instructions for PubMed e-mail alerts.
Depending on how long it is taking you to carry out the systematic review, you will need to update your literature search to include the latest evidence. If you have saved your search strategies in the respective databases, then it should not be difficult to re-run the search with new date limits. The literature search should be updated prior to being submitted for publication.