Table 4-2 shows examples of how the PICO format can guide the building of a research question.

The characteristics of the study population, such as age, sex, severity of illness, and presence of comorbidities, usually vary among studies and can be important factors in the effect of an intervention. Health care interventions may have numerous outcomes of interest. The research question should be formulated so that it addresses all outcomes—beneficial and adverse—that matter to patients, clinicians, payers, developers of practice guidelines, and others who may be affected (Schünemann et al., 2006). For example, treatments for prostate cancer may affect mortality; but patients are also interested in learning about potential harmful treatment effects, such as urinary incontinence and impotence. Imaging tests for Alzheimer’s disease may lead to the early diagnosis of the condition, but patients and the patients’ caregivers may be particularly interested in whether an early diagnosis improves cognitive outcomes or quality of life.

Many researchers suggest that decision makers be directly involved in formulating the question to ensure that the systematic review is relevant and can inform decision making (Lavis et al., 2005; Schünemann et al., 2006). The questions posed by end users must sometimes be reframed to be answerable by clinical research studies.

TABLE 4-2 PICO Format for Formulating an Evidence Question

PICO Component

Tips for Building Question


Patient population or problem

“How would I describe this group of patients?”

  • Balance precision with brevity

“In patients with heart failure from dilated cardiomyopathy who are in sinus rhythm …”

Intervention (a cause, prognostic factor, treatment, etc.)

“Which main intervention is of interest?”

  • Be specific

“… would adding anticoagulation with warfarin to standard heart failure therapy …”

Comparison intervention (if necessary)

“What is the main alternative to be compared with the intervention?”

  • Be specific

“… when compared with standard therapy alone …”


“What do I hope the intervention will accomplish?” “What could this exposure really affect?”

  • Be specific

“… lead to lower mortality or morbidity from thromboembolism? Is this enough to be worth the increased risk of bleeding?”

SOURCE: Adapted from the Evidence-based Practice Center Partner’s Guide (EPC Coordinating Center, 2005).

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