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Evidence Based Medicine (EBM)

This guide is designed to walk you through the Evidence Based Medicine process: the elements of a well-formulated clinical question, types of studies, and the key critical appraisal questions that help determine the validity of evidence.

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Clinical questions are usually complex, multifaceted, and arise frequently in the course of daily clinical practice. Finding answers to each question can be problematic for the health practitioner due to: 

  • clinical practice time pressures
  • a lack of awareness of high quality resources for finding research evidence
  • perceived or real lack of searching skills
  • the sheer size of the clinical research literature:
    • > 23 million citations in PubMed alone [1]
    • thousands of new studies published weekly
    • 75 RCTs and 11 SRs published daily [2].

An efficient method for tackling clinical questions is to:

  1. Convert the question into a manageable, answerable format using the PICOS mnemonic
  2. Rephrase the question simply based on its PICOS
  3. Develop a 'logic grid' using the core concepts of the question
  4. Explore synonyms for each core concept in preparation for constructing an efficient, effective search strategy.

An example of a clinical scenario that needs converting to a PICOS


Roger, a 26 year old student, has been diagnosed with major depression. He has tried three different antidepressant medications in the past with no improvement. Reluctant to try a further prescribed medication he asks about non-pharmacologic alternatives. You have heard that repetitive transcranial magnetic stimulation has been trialed for treatment resistant depression but you are not sure if its effectiveness has been proven. You tell Roger that you will look into this for him.
 

Go to the PICOS tab above to see how this scenario can be converted into a well-structured question.


1. U.S. National Library of Medicine. Fact sheet: MEDLINE, PubMed, and PMC (PubMed Central): How are they different? [Internet]. Bethesda, MD: U.S. National Library of Medicine; 2002 [updated 2014 May 7; cited 2015 Apr 28]. Available from: http://www.nlm.nih.gov/pubs/factsheets/dif_med_pub.html

2. Bastian H, Glasziou P, Chalmers I. Seventy-five trials and eleven systematic reviews a day: how will we ever keep up? PLoS Med. 2010 Sep; 7(9): e1000326.

What is PICO(S)?

PICO(S) is an established EBM tool that helps you clarify a specific problem, identify a gap in your own knowledge, and then formulate a clearly focused clinical question in preparation for searching for an answer.


Step 1. Turn a clinical scenario into a PICOS

Roger, a 26 year old student, has been diagnosed with major depression. He has tried three different antidepressant medications in the past with no improvement. Reluctant to try a further prescribed medication he asks about non-pharmacologic alternatives. You have heard that repetitive transcranial magnetic stimulation has been trialed for treatment resistant depression but you are not sure if its effectiveness has been proven. You tell Roger that you will look into this for him.


This clinical scenario can be expressed as the following PICOS.

Patient Intervention Comparison Outcomes Study designs
Patient with treatment-resistant, (non-psychotic) depression Repetitive transcranial magnetic stimulation No transcranial magnetic stimulation Reduction in depression severity or remission RCTs or systematic reviews of RCTs

 

 

 

 


Step 2. Turn the PICOS into a well-formulated question

This PICOS above can be succinctly and clearly articulated as: In patients with treatment-resistant, non-psychotic depression, is repetitive transcranial magnetic stimulation beneficial in reducing depression severity and effecting remission?


Step 3. Create a logic grid for the question

Once you have clarified your question by creating a PICOS structure for it, transfer the significant concepts in your PICO to a Logic Grid.

The Logic Grid will help you:

  • identify the concepts in your question which need to searched on for your search to have a minimum level of precision
  • clarify which concepts can be left out of the search, or added later if required to improve precision
  • prepare for finding appropriate and useful synonyms, acronyms, variant spellings etc. for each concept.
     
Concept 1:
Treatment-resistant depression
Concept 2:
Repetitive transcranial magnetic stimulation
  • Treatment-resistant depression/depressive disorder
  • Treatment-resistant major depressive disorder
  • Treatment-resistant MDD
  • Treatment-refractory depression/depressive disorder
  • Pharmacoresistant depression/depressive disorder
  • Medication-resistant depression/depressive disorder
  • Repetitive transcranial magnetic stimulation
  • rTMS
  • Deep repetitive transcranial magnetic stimulation
  • DTMS


Now go to the Intervention (therapy) question section of this guide to see how this question is developed into a search strategy and the critical appraisal questions that need to be asked.


A further PICO example

A further Logic Grid example