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Evidence Based Medicine Guide: PICO & the Question Statement

The PICO Framework

The PICO framework is often recommended as a way to structure and focus clinical questions. PICO can make it easier to identify search concepts and appraise the results retreived from database searches.

PICO stands for

  • Patient and Problem 
  • Intervention or exposure
  • Comparison or Control
  • Outcome

When you break down your question using PICO, keep the following points in mind:


  • Your Patient is a member of a population as well as a person with (or at risk for) a health problem. In addition to age and sex, you may also need to consider ethnicity, socioeconomic status or other demographic variables when you look for and evaluate the evidence.
  • A Comparison is not always present in a PICO analysis. If you are evaluating the utility of a diagnostic test, though, you will need to compare the new test to the "reference standard".
  • Outcomes should be measurable: the best evidence comes from rigorous studies with statistically significant findings.
  • Outcomes ideally measure quality of life or clinical well being, and not surrogate markers such as laboratory test results.


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


Question Type Patient, Problem Intervention or Exposure Comparison Outcome Measures
The patient's disease or condition. A therapeutic measure, ex., a medication, surgical intervention, or life style change. Standard of care, another intervention, or a placebo. Ex: mortality rate, days lost from work, pain, disability.

The patient's risk factors and general health condition. A preventive measure, e.g., a medication or a life style change. May not be applicable. Ex: disease incidence, mortality rate, days lost from work.
Diagnosis The target disease or condition. A diagnostic test or procedure. The current "reference standard" or "gold standard" test for the problem. Measures of the test utility, ex., sensitivity, specificity, odds ratio.
Prognosis (Natural History) The main prognostic factor or clinical problem in terms of its severity and duration. The exposure of interest is usually time, sometimes expressed as "watchful waiting". Usually not applicable. Identify the standard treatment if your question is about "watchful waiting". Ex: survival rates, mortality rates, rates disease progression.

Etiology or

Your patient's risk factors, current health disorders or general health condition The intervention or exposure of interest, including some indication of the strength (dose) of the risk factor and the duration of the exposure. May not be applicable. Ex: disease incidence, rates of disease progression, mortality rates.

The Question Statement

If you have clearly identified the main elements of your question using the PICO format, it will be easy to write your question statement.  The examples, below, are based on cases drawn from the second edition of the Users' Guides to the Medical Literature: A Manual for Evidence-Based Clinical Practice [Online] (1).  Note that to improve the flow of the question statements, we have placed the comparison, if any, after the outcome.

Question Type Patient & Problem Intervention or Exposure Outcome Comparison
Therapy In adult intravenous drug users with endocarditis Are oral antibiotics As effective in treating infection and reducing complications or mortality As intravenous antibiotics?
Prevention In hypertensive adult women who have type 2 diabetes without diabetic complications Does a target diastolic blood pressure (DBP) of 80 mm hg Lower risk of stroke, MI, or cardiovascular death Compared with a target DBP of 90 mm hg?
Diagnosis In older patients with suspected cognitive impairment Does a brief screening tool for dementia Have sensitivity, specificity and predictive values Similar to those of the standard screening tool, the MMSE?
Prognosis In middle-aged patients who present with transient loss of consciousness Within the year after presentation What is the relative risk of morbidity (such as seizures or strokes) or death?  
Etiology or Harm Do adults Who binge drink Have higher mortality rates Than those who do not binge drink?


(1) Guyatt G, Meade MO, Richardson S, Jaeschke R. Chapter 3. What is the question? In: Guyatt G, Rennie D, Meade MO, Cook DJ, eds. Users’ Guides to the Medical Literature: A Manual for Evidence-Based Clinical Practice. 2nd ed. New York, NY: McGraw-Hill; 2008.