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Evidence Based Medicine: The PICO Framework

An overview on evidence based medicine (EBM) including resources and training materials

Asking Focused Questions

"One of the fundamental skills required for practising EBM is the asking of well-built clinical questions. 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 answers1."

Natural language questions typically do not contain the elements of clearly formulated question and can lead to difficulty when trying to find an answer.2,3 A modest investment of time to consider what you need to find out and construct a focused question will yield a more effective and efficient search for evidence, helping you to more quickly locate the best available evidence to inform your decision.  

The PICO Framework

The PICO framework is the most commonly used model for structuring clinical questions because it captures each key element required for a focused question. PICO stands for:

  • Patient or problem 
  • Intervention or exposure
  • Comparison or control
  • Outcome(s)

The table below illustrates ways in which problems, interventions, comparisons and outcomes vary depending on the type (domain) of your question.

Question Type Patient or Problem Intervention or Exposure Comparison Outcome Measures
Therapy The patient's disease or condition. A therapeutic intervention, ex., a drug, surgical intervention, medical advice. Standard care, another intervention, or placebo. Ex: Mortality rate, complications, disease recurrence.
Diagnosis The target disease or condition. A diagnostic test or procedure. The current "reference standard" test for the problem. Measures of the test utility, ex., sensitivity, specificity.
Prognosis The main prognostic factor or clinical problem in terms of its severity and duration. The intervention or exposure of interest, ex. a disease, drug, or time.

Standard care, another intervention, or placebo for interventions.

Absence of exposure for exposures.

May not be applicable, particularly if exposure of interest is time.

 Ex: Rates of survival, mortality or disease progression.

Etiology or
Harm
 

 Your patient's risk factors, current health disorders or general health condition The intervention or exposure of interest, ex. a disease, drug, or time, including some indication of the strength (dose) of the risk factor and the duration of the exposure.

Standard care, another intervention, or placebo for interventions.

Absence of exposure for exposures.

May not be applicable.

Ex: Disease incidence, rates of disease progression or rates.
Prevention The patient's risk factors and general health condition. A preventive measure, e.g., a medication or a lifestyle change. Absence of preventive measure. May not be applicable. Ex: Disease incidence, mortality rate, days lost from work.

When constructing your PICO question, a few important points to bear in mind:

  • Your patient is a member of a population as well as a person with (or at risk for) a health problem.
    • Factors to consider include age, sex, comorbid conditions, past medical history, socioeconomic status or other demographic variables, as these factors may impact your patient's risk level.
    • You need to assess what reasonable clinical study population your patient could be part of. For example, if your patient is a 73 year old woman, "73 year old women" or "women in their 70s" is too specific because it is highly unlikely that clinical researchers would design a study that would exclusively enroll women in their 70s. Depending on the nature of your question, a reasonable population might be something like "post-menopausal women" or "older adults."
  • Outcomes must be measurable and ideally measure clinically important outcomes rather than surrogate markers such as laboratory test results.

The Question Statement

Once you have identified the main elements of your question using the PICO format, it will be easier to write your question statement. To improve the flow of the question statements, we have placed the comparison after the outcome in the examples below.

Question Type Patient or Problem Intervention or Exposure Outcome Comparison
Therapy In patients with hypertension and at least one additional cardiovascular disease risk factor Does tight systolic blood pressure control Lead to lower rates of myocardial infarction, stroke, heart failure, and cardiovascular mortality Compared to conservative control?
Diagnosis Among asymptomatic adults at low risk of colon cancer Is fecal immunochemical testing (FIT) As sensitive and specific for diagnosing colon cancer As colonoscopy?
Prognosis Among adults with pneumonia Do those with chronic kidney disease (CKD) Have a higher mortality rate Than those without CKD?
Etiology or Harm Are women With a history of pelvic inflammatory disease (PID) At higher risk for gynecological cancers Than women with no history of PID?
Prevention Among adults with a history of myocardial infarction Does adherence to a  mediterranean diet Lower risk of a second myocardial infarction Compared to those who do not adopt a mediterranean diet?