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Centre for Evidence-
Based Medicine

Formulating Answerable Clinical Questions (Page 2)

When this patient scenario was encountered on our clinical service, the housestaff generated several clinical questions including:

  1. Can ASA decrease the risk of stroke?
  2. Does a carotid bruit predict significant carotid stenosis?
  3. How effective is a carotid endarterectomy in someone with moderate carotid stenosis?

Note that these questions ask for specific knowledge about the diagnosis and management of the patient. Well-built clinical questions should have 4 components:

Patient or Problem Intervention Comparison Intervention Outcome
Description of the patient or the target disorder of interest Could include:
  • Exposure
  • Diagnostic test
  • Prognostic factor
  • Therapy
  • Patient perception etc.
Relevant most often when looking at therapy questions Clinical outcome of interest to you and your patient

Returning to the 3 questions that we posed above, how can we make them into well-built clinical questions?

Let's look at the first question:

Patient or Problem Intervention Comparison Intervention Outcome
65 year old man with a stroke and moderate carotid stenosis ASA Placebo Stroke

Now we can use this to formulate our clinical question:

In a 65 year old man with a stroke and moderate carotid stenosis, can ASA decrease the risk of another stroke compared with no treatment?

Try formulating a well-built question yourself using the last 2 questions that were posed by our housestaff, and then you can print this page.

  1. Does a carotid bruit predict significant carotid stenosis?

    Patient or Problem Intervention Comparison Intervention Outcome


    Compare this to the question we formulated

    Patient or Problem Intervention Comparison Intervention Outcome
    65 year old man with a stroke Carotid bruit Doppler ultrasonography or angiography Carotid stenosis
    In a 65 year old man with a stroke, how precise and accurate is the presence of an ipsilateral carotid bruit for diagnosing significant carotid stenosis compared with doppler ultra sonography?

    Note: there are other variations of this question; for example, we could have asked about angiography.

  2. How effective is a carotid endarterectomy in someone with moderate carotid stenosis?

    Patient or Problem Intervention Comparison Intervention Outcome


    Compare this to the question we formulated

    Patient or Problem Intervention Comparison Intervention Outcome
    65 year old man with stroke and moderate carotid stenosis Carotid endarterectomy Medical therapy Stroke
    In a 65 year old man with stroke and moderate carotid stenosis, can carotid endarterectomy decrease the risk of stroke compared with medical therapy?

    Note: there are variations for this question; for example we could have asked about other outcomes like death.