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Evidence-Based Medicine: Ask a Clinical Question

This is a libguide for praticing evidence-based medicine.

Type of Questions

Clinical questions arise around the central issues involved in caring for patients. It is helpful to narrow down the type of clinical question you are asking. There are four main types of clinical questions:

    1. Therapy: questions concerning the effectiveness of a treatment or preventative measure.

    2. Harm/Etiology:  questions concerning the likelihood of a therapeutic intervention to cause harm.

    3. Diagnosis: questions concerning the ability of a test to predict the likelihood of a disease.

    4. Prognosis questions concerning the future course of a patient with a particular condition.

Why Spend Time Formulating Questions?

Well-formulated questions can help in many ways:

1. They help you focus on evidence that is directly relevant to patients’ clinical needs.

2. They help you focus on evidence that directly addresses clinicians' or learners' knowledge needs.

3. They can suggest high-yield search strategies.

4. They suggest the forms that useful answers might take.

5. They can help to communicate more clearly with clinicians and facilitate education and learning.

PICOTS Framework for Clinical Questions

When well built, clinical questions usually have four components:

P: The patient situation, population, or problem of interest.
I: The main intervention, defined very broadly, including an exposure, a diagnostic test, a prognostic factor, a treatment, a patient  perception and so forth.
C: A comparison intervention or exposure (also defined very broadly), if relevant.
O: The clinical outcome(s) of interest, including a time horizon, if relevant.

In addition to the standard PICO components, the broader PICOTS framework is extremely useful and important for defining key clinical questions and assessing whether a given study is applicable or not. T refers to Timing and S refers to Setting or Study Design.

T: Timing, i.e. the time it takes to demonstrate an outcome OR the period in which patients are observed.
S: Setting (e.g. ambulatory settings including primary, specialty care and inpatient settings), or sometimes Study Design (such as a randomized controlled trial).

Reference: Matchar DB. Introduction to the Methods Guide for Medical Test Reviews. AHRQ Publication No. 12-EHC073-EF. Chapter 1 of Methods Guide for Medical Test Reviews (AHRQ Publication No. 12-EHC017). Rockville, MD: Agency for Healthcare Research and Quality; June 2012.

You can use the Research Medical Library's PDF template linked above to help formulate a clinical question. Other resources for formulating clinical questions include:

PICO(T) Templates (McMaster University Health Sciences Library)

Example for Therapy question:

In ___[P]___,  do/does ___[I]___ result in ___[O]____ when compared with ___[C]___ over ___[T]____?

E.g.) In nursing home residents with osteoporosis, do hip protectors result in fewer injuries from slips, trips, and falls when compared with standard osteoporosis drug therapy over the course of their stay?

PICO Form (National Library of Medicine)

The PICO form linked above can be used to search medical literature with your PICO terms.

Find Studies

Which type of question you're asking determines which type of study is most appropriate to consult.

Question Type Study Design
Therapy randomized controlled trial > cohort study
Harm/Etiology cohort study > case control > case series
Diagnosis prospective, blind comparison to a gold standard or cross-sectional
Prognosis cohort study > case control > case series