Filtered Resources

When searching for evidence-based information, begin by searching for the highest level of evidence possible, which is considered to be systematic reviews or meta-analyses where 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.

Unfiltered Resources
Information that has not been critically appraised is considered "unfiltered". You’ll also need to search unfiltered resources (the primary literature) to locate studies that answer your question.

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 to determine its validity and applicability to the patient or the practice question.

Meta-Analysis

Systematic Reviews/Meta-Analyses

Evidence Synthesis/Guidelines, Summaries (Critically Appraised Topics)

Critically Appraised Individual Articles/E-Journals

Individual Research Studies

Background Information (Cross-searchable resources including online textbooks, reference sources)

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.

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' would have been assigned to all three articles, making all three articles easy to find 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. One example might be: [sepsis NOT mice], which would eliminate articles on 'sepsis in mice.'

Different types of clinical questions are best answered by different types of research studies. Understanding what types of studies are best suited for your question can improve your search for information to answer your question.

All types of clinical questions can be answered by systematic reviews or meta-analyses, when available. When these filtered resources are not available, look for unfiltered resources (individual studies), focusing on the study types appropriate to your question. The table below suggests study designs best suited to answer each type of clinical question.