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Evidence-Based Medicine: Step 1: Ask

The first step of EBM is to construct a guiding question. 

According to the Centre for Evidence Based Medicine (CEBM), well-formed clinical questions are essential to practicing EBM. "To benefit patients and clinicians, such questions need to be both directly relevant to patients' problems and phrased in ways that direct your search to relevant and precise answers." (CEBM, University of Oxford, Asking Focused Questions)

Example PICO Question

In a 30-year old male patient diagnosed with depression (P), what is the effect of St. John's wort (I), as compared to SSRIs (C), on reducing depressive symptoms (O) in one year (T)?

Find more examples here:


The PICO format helps you

  • form an appropriate, focused question
  • identify key concepts and brainstorm search terms
  • develop a strong search strategy
  • obtain a manageable number of pertinent results
  • appraise results for relevance

Adapted from Developing a PICO Question Tutorial: Part 1 of a 2 part tutorial series from Marymount Library's PICO Tutorials

What is PICO?

The PICO model can help you formulate a good clinical question. Sometimes it's referred to as PICO-T, containing an optional 5th factor. 

 P - Patient,  Population, or  Problem

 What are the most important characteristics of the   patient?

 How would you describe a group of patients similar to   yours?

 I - Intervention,  Exposure,  Prognostic Factor

 What main intervention, prognostic factor, or exposure   are you considering?

 What do you want to do for the patient (prescribe a  drug, order a test, etc.)?

 C - Comparison  What is the main alternative to compare with the   intervention? 
 O - Outcome  What do you hope to accomplish, measure, improve, or   affect?
 T - Time Factor,  Type of Study  (optional)

 How would you categorize this question?

 What would be the best study design to answer this   question? 

PICO Resources

Alternative Frameworks

Although PICO is the most widely used framework for generating a question, there are some situations in which you might find that a different framework is more appropriate. Here are a few alternatives.

  • PEO: Population, Exposure, Outcome (Useful for public health and qualitative studies)
  • SPICE: Setting, Perspective, Intervention, Comparison, Outcome (Useful for qualitative studies and evaluating projects)
  • SPIDER: Sample, Phenomenon of Interest, Design, Evaluation, Research Type (Useful for topics focused on samples rather than populations)
  • PIPOH: Population, Intervention, Profession, Outcome, Health Care Setting (Useful for screening and creating practice guidelines)
  • PICo: Population, Intervention, Context
  • PIT or PICTO: Population, Index test, (Comparator,) Target condition, (Outcome) (Used for diagnostic test accuracy)
  • ECLIPSe: Expectation, Client group, Location, Impact, Professionals, Service (Useful for studying outcomes of policies or services)