Skip to Main Content

Applied Evidence Based Medicine


  • Understand how to use PICO to formulate an etiology question
  • Become familiar with resources for understanding etiology studies
  • Know where to look for harm calculators

PICO for Etiology Questions

When using PICO to frame an etiology question, the P is the patient or population; the I is exposure to certain conditions or risk behaviours; the is lack of exposure to those conditions or risk behaviours; and the O is the outcome of interest, such as the development of a certain disease or condition. 

Here are a couple of examples of how you would form an answerable etiology question using PICO:


Scenario 1: You have recommended hormone replacement therapy (HRT) to your 55-year-old patient to relieve the symptoms of menopause that she's experiencing. She has heard about the correlation between HRT and breast cancer and wants to know more. You consult the medical literature to find evidence-based resources. 

P: menopausal women

I: hormone replacement therapy

C: (not applicable)

O: increased risk of breast cancer

Clinical Question: To what extent is hormone replacement therapy associated with risk of breast cancer in menopausal women?


Scenario 2: You have a 39-year-old patient who has experienced very heavy bleeding for much of her life. After exploring all the other options, you discuss the possibility of a hysterectomy as a solution, but you wonder if her high blood pressure might increase her risk of acute myocardial infarction in the year following surgery. What does the literature say?

P: 39-year-old woman undergoing hysterectomy

I: high blood pressure

C: normal blood pressure

O: increased risk of acute myocardial infarction

Clinical Question: Are women who have high blood pressure compared with those without high blood pressure at increased risk for an acute myocardial infarction during the first year after hysterectomy?

Resources for Understanding Etiology Studies

Harm Calculators