Evidence Based Medicine: Formulating Questions

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Converting the patient dilemma into a well-built clinical question

When a clinical question arises from the care of a patient, the first step in the EBM process is to formulate a question. A well formulated question facilitates a literature search strategy that results in literature relevant to the patient question.

Using PICO to formulate a clinical question

One template for formulating a clinical question is the PICO model developed by W. Richardson. According to Richardson (1995) the question should be phrased to facilitate searching for a precise answer. To achieve these aims it has been proposed that the question must be complete and composed of all 4 parts of its anatomy:

P the patient or problem being addressed How would you describe a group of patients similar to yours? May include the primary problem, disease, or co-existing conditions, gender, age or race.
 I  the intervention or exposure being considered What is the intervention or treatment being considered for this patient or problem? This may be a treatment, therapy, or product/protocol recommendation.
C the comparison intervention or exposure, if relevant  What is the main alternative to compare with the intervention? Are you trying to decide between two drugs, a drug and no medication or placebo, or  two diagnostic tests? Your clinical question may not always have a specific comparison.
O the clinical outcome
of interest
What can you hope to accomplish, measure, improve or affect? What are you trying to do for the patient? Relieve or eliminate the symptoms? Reduce the number of adverse events? Improve function or test scores?
 PICO image Additional questions to ask
  • What type of question are you asking?- Diagnosis, Etiology/harm, Therapy, Prognosis, Prevention
  • What type of study do you want to find?-What would be the best study design/methodology?

View detailed case examples of PICO questions.

Additional questions to ask concerning study designs

In addition to PICO, there are two additional questions that are helpful: 1) What type of question are you asking? Determining this will help you answer 2) What type of study do you want to find? Use the chart below to guide you.

Type of question Suggested study type
Diagnosis– how to select and interpret diagnostic tests
  • prospective
  • blind comparison to a gold standard or cross-sectional
Therapy– how to select treatments that do more good than harm
  • randomized controlled trial
  • cohort study
  • double-blind
Prognosis– how to estimate the patient’s likely clinical course over time and anticipate complications
  • cohort study
  • case control
  • case series
Etiology or Harm– concerning causes or contributing factors of disease
  • cohort
  • case control
  • case series
Prevention– how to prevent disease
  • randomized controlled trial
  • cohort study
Quality Improvement– how can the quality be improved based on client health and professional experience
  • randomized controlled trial



Tools for building a
clinical question

Article: The well-built clinical question: a key to evidence- based decisions. Richardson W.S. et al. ACP J Club. Nov-Dec 1995; 123(3):A12-13.