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.