The second step in the process is deciding which type of information resource would be the most appropriate to support your information needs. Information resources fall into two broad categories: filtered and unfiltered.
When searching for evidence-based information, it is wise to begin by searching for the highest level of evidence possible, which is considered to be systematic reviews or meta-analyses. Systematic reviews, meta-analyses, and critically-appraised topics/articles have all gone through an evaluation process: they have been "filtered". With filtered resources, the literature on a topic has already been searched to provide the best answer to a clinical question or practice issue.
In other words, experts have 1) located all the available evidence they could find on a topic from individual studies and reports; 2) analyzed the validity and reliability of the studies to determine whether each study should be included; and 3) summarized the findings from the available research to present the data, conclusions and recommendations for clinical questions and nursing practice based on the best available evidence. The most appropriate resources for finding filtered resources are:
Information that has not been critically appraised is considered "unfiltered". If you don’t find an appropriate answer in the filtered resources, you’ll need to search unfiltered resources (the primary literature) to locate studies that answer your question. Additionally, you may choose to search the unfiltered resources to see if any new research has been done since the conclusions reached in the filtered resources were released.
Unfiltered resources are individual articles that provide the most recent information from clinical and practice research, such as case studies, comparative studies, or clinical trials. With unfiltered resources, it is up to the nurse to evaluate each study s/he found to determine its validity and applicability to the patient or the practice question. The most appropriate databases for finding unfiltered resources are:
Once you choose your database, you will need to combine the search terms you chose using the PICO(T) method in Step 1. This is often done by selecting matching subject headings in the database and by using AND, OR, and NOT to combine the search terms. For more in-depth training on the basics of searching, go to: Search Basics for the Health Sciences
While the methods of finding and selecting subject headings varies slightly between databases, the principles are the same:
Subject headings are controlled vocabulary created by organizations to give consistency to the way that literature is described. Often, the initial words chosen when constructing a PICO(T) question are simply keywords, which are natural language words and not used consistently by all researchers who produce literature. Whenever possible, locate and use the subject headings within a database in order to search for articles. An example of the difference is:
In this example, one researcher may use the term 'childbirth', another researcher uses the term 'birth' and another researcher uses the term 'parturition'. All three researchers are describing the same concept, but using different terms to do so. Within a database, a subject heading of 'Parturition' [the MEDLINE subject heading in this example] would have been assigned to all three articles, making all three articles findable with the subject heading. Without this subject heading, if you had searched using the keyword 'birth', you probably would have missed the articles in which the researchers had used either 'childbirth' or 'parturition'.
Using subject headings helps you to retrieve articles that are more relevant to your question, while gathering in articles that keyword searching would have missed.
AND, OR, NOT are used to combine search terms (keywords or subject headings) within a database.
AND is used when you want an article to contain both (or several) concepts--it tells the database that you only want articles that include all your terms. E.g. [Sutures AND staples AND pain] would only give you articles that discuss all three of those keywords or concepts.
OR is used when you want articles on two different concepts or think more than one keyword or subject heading would be appropriate. E.g. [(Sutures OR staples) AND pain] would give you articles that either discuss just sutures AND pain as well as articles that just discuss staples AND pain. Notice that the words with an OR between them live inside parentheses, which is necessary in order for the database to interpret your search correctly. Keep this in mind when using OR.
NOT is used to exclude concepts from searches, however, using NOT often results in missed articles. Use NOT very cautiously. One example might be: [sepsis NOT mice], which would eliminate articles on 'sepsis in mice.'
|Type of Question||Suggested Research Design(s)|
|All clinical questions||Systematic review, meta-analysis|
|Therapy||RCT > cohort > case control > case series|
|Etiology/Harm||RCT > cohort > case control > case series|
|Diagnosis||Prospective, blind comparison to a gold standard|
|Prognosis||Cohort study > case control > case series|
|Prevention||RCT > cohort study > case control > case series|
Questions of therapy and prevention which can best be answered by an RCT can also be answered by a meta-analysis or systematic review.
If you are having trouble with specific databases, Laupus Library has tutorials available for some of our major research databases. The collection of tutorials may be browsed here: Laupus Help Sheets
For one-on-one help, please contact your liaison librarian. We are willing to meet with you via phone, virtual face-to-face programs (e.g. Skype, Google Hangouts, etc.) or in person.