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Evidence-Based Practice for Nursing: Finding Evidence

Step One: Translating the Question into Searchable Parts: PICO(T)

Clinical and nursing practice questions can be broken down into essential components to make the information-seeking process easier. The most common way to begin is to use the PICO(T) format, which breaks a question apart into searchable parts. Please note that not all parts are required. PICO(T) stands for:

P – Patient, population, problem
I – Intervention or Exposure
C – Comparison (optional)
O – Outcome (optional)
T – Time (optional)

Example (adapted from Haddock, 2005): An elderly female patient is in the hospital for a few days after a joint replacement. The nurses notice that the patient is not sleeping much or well at night. When the patient refuses medication to induce sleep, the nurses must find alternate methods of addressing the patient’s sleeplessness. The question might be: 'how does [alternative method of sleep inducement] compare to soporifics?', which can be broken apart into descriptors, written in noun forms, such as:

  • P – female, elderly, inpatient, insomnia
  • I – earplugs or complimentary therapy to reduce anxiety and/or sleep interruptions (depends on the root causes of the lack of sleep, determined by observation)
  • C – soporifics
  • O – to be determined once the literature has been found and in conjunction with an understanding of the patient’s specific situation and the underlying causes of sleep loss.
  • T--not applicable in this example

A worksheet to assist you in breaking your question apart using PICO can be found here: PICO Worksheet, (below).

Step Two: Choosing the Database: Filtered vs. Unfiltered Resources

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.

Filtered Resources

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:

Unfiltered Resources
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:

Step Three: Combining Search Terms to Locate Information (an overview)

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.'


Step Four: Selecting the Best Study Types to Answer Your Question

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.

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
Cost Economic analysis

Questions of therapy and prevention which can best be answered by an RCT can also be answered by a meta-analysis or systematic review.

Help Using Specific Databases

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.