Presentation given to second year medical students at McGill University.

1. Evidence-Based Medicine
(EBM)
INDS 301, Jan. 2013
Prosanto Chaudhury, MD, MSc, FRCSC, FACS
Robin Featherstone, MLIS

2. Objectives
By the end of the lecture, you will be able to:
1. Describe objectives and expectations for the
course
2. Describe the five stages of the EBM process
3. Differentiate between background and
foreground questions
4. Describe the components of a PICO question
5. Categorize PICO questions and identify the best
studies to answer each question type

3. EBM Course Contents
Format Content
Lecture 1 Overview of the course and an introduction to EBM, PICO
question formation, and EBM resources
Workshop Searching EBM resources
Small group 1 PICO question formation
Lecture 2 Critical appraisal of randomized controlled trials (RCT) and
systematic reviews (SR)
Small group 2 Appraisal of a RCT
Small group 3 Appraisal of a SR
Small group 4 Appraisal of a diagnostic test study
Course website: http://www.jamaevidence.com/

4. Evaluation
Item Description Weight
Small Groups 4 interactive sessions with clinical tutors. 40%
Evaluation based on participation.
Assignment 3 pages including: 30%
• Clinical scenario
• PICO
• Search strategy
• Name of chosen paper
• Critical appraisal
• Your conclusion
OSCE 15 minute station: 30%
• Develop a question based on a clinical scenario
• Perform a search based on your question

5. Introduction to EBM
Why are we doing this?

6. Why is EBM important?
“Evidence-based medicine is the integration of best
research evidence with clinical expertise and patient
values”
Patient - Dave Sackett
Concerns
EBM
Best research Clinical
evidence Expertise
Slide courtesy Prof Paul Glasziou, CEBM

7. EBM in practice
• Took an “evidence cart” on rounds - 1995
• Looked up 2-3 questions per patient
• Took 15-90 seconds to find evidence
• Changed about 1/3 decisions
• Rounds took longer!
Dave Sackett

8. Challenges to practicing EBM
RCTs published over the last 50 years
20000
18000
16000
14000
12000
RCTs
10000
8000
6000
4000
2000
0
1960 1970 1980 1990 2000 2010
Source: PubMed data for "randomized controlled trial"[Publication Type]

9. How I use EBM

10. How you can use EBM
• Keep a logbook of questions
• Answer a few important questions
• Identify important knowledge gaps
• Discuss and share evidence with colleagues (journal
club)

11. EBM Process
Formulating
Evaluating the clinical
Assess Ask
the Process question
Your patient for whom
you are uncertain about
therapy, diagnosis, or Searching
Incorporating prognosis the Evidence
evidence into
decision-making Acquire
Appraise
Apply
Appraising
the Evidence

12. EBM Question Formation
1. Background vs Foreground

13. Can a 70 year old
pancytopenic patient with
suspected meningitis
receive platelets before
undergoing a lumbar
puncture?
What is pancytopenia?
What is the diagnostic test
for meningitis?
[1.]
Guyatt G, Rennie D, Cook D. Users' Guides to the Medical Literature : A Manual for Evidence-Based Clinical Practice (2nd Edition). New
York, NY, USA: McGraw-Hill Professional Publishing; 2008.
Ask

14. A 25 year-old female has been recently diagnosed with
classical Hodgkin’s lymphoma (nodular sclerosing subtype).
Staging reveals that she is a stage IIA with a 4.5 cm nodal
mass in her neck and mediastinal nodes. Her hematologist
recommends combined modality therapy
(chemotherapy/radiation therapy). The patient has done
some reading about therapy and is worried about the long
term effects of radiation especially the risk of breast cancer.
Background Foreground
What is the pathophysiology of For a 25 year old female with
Hodgkin’s lymphoma? stage IIA Hodgkin’s lymphoma,
is combined modality therapy
superior to chemotherapy
alone?
Ask

15. A 35 year-old patients presents to the ER with a left leg swelling x
3 days. The patient recently returned from a business trip in
Malaysia and therefore you suspect a deep vein thrombosis
(DVT). It is the weekend and so the patient receives a CT
angiogram that does not reveal any pulmonary embolism and the
venous portion of the study does not reveal any above or below
knee clots. That said, you are still convinced that the patient may
have a lower limb DVT and so you ask for a lower limb doppler
which requires the radiologist to come into the hospital in the
middle of the night to perform the study. The radiologist is
reluctant to come as the venous phase of the CT angiogram was
negative.
Discuss with your
neighbour. Record one
background and one
foreground question.
Creative copyright image. Attribution: James Heilman, MD. Accessed from Ask
http://upload.wikimedia.org/wikipedia/commons/0/0a/DVT2010.JPG

16. Background
Questions
Sources for Background Questions (AKA “Filtered Information”)
• Textbooks
• Handbooks
• Manuals
• etc
[1.]
Acquire

17. EBM Question Formation
2. P.I.C.O.
Patient, Population, or Problem
Intervention or exposure
Comparison
Outcome

18. Simple
You have been asked to review the
practice guidelines for treating warts. You
are confident that cryotherapy is the most
effective treatment but a colleague
suggested some alternatives to
investigate, including duct tape.
Ask

19. Simple
Patient, Population, or Patients with common warts
Problem
Intervention or Duct tape
exposure
Comparison Cryotherapy
Outcome Eliminating warts
Answerable clinical question:
In patients with common warts, is duct tape as effective as
cryotherapy in eliminating warts?
Ask

20. Intermediate
You are following a 35 year-old pregnant female for low
platelets thought to be due to immune thrombocytopenia as
she had thrombocytopenia prior to her pregnancy. She
undergoes a delivery without complications. She and the
baby are medically ready to leave the hospital 48 hours
later. She asked if she should be concerned for her
newborn, knowing that her antibodies, the same that are
causing her immune thrombocytopenia, are passed along
to the baby.
Ask

21. Intermediate
Patient, Population, or Newborns with suspected immune thrombocytopenia
Problem
Intervention or Blood test to check platelets
exposure
Comparison No blood test
Outcome Diagnosis of immune thrombocytopenia
Answerable clinical question 1:
For newborns with suspected immune thrombocytopenia, is a blood test to determine
platelet count recommended to diagnose immune thrombocytopenia?
Answerable clinical question 2:
For newborns with suspected immune thrombocytopenia, when should a blood test
be given to diagnose immune thrombocytopenia?
Ask

22. Best studies to answer each
question type

23. Question Best Evidence
Cost • Cost-effectiveness study
Diagnosis • Diagnostic validation studies
• Prospective studies / blind comparison to a
gold standard
Etiology/Harm • Cohort study
• Case control study
Prognosis • Cohort study
• Case control study
Quality of life • Qualitative studies
Therapy • Systematic review of Randomized Controlled
Trials (RCTs)
• Single RCT
1
2
Heneghan, Carl, and Douglas Badenoch. Evidence-Based Medicine Toolkit. 2nd ed. Malden, Mass.: BMJ Books/Blackwell Pub., 2006.
Glover, Jan, and Lei Wang. Find it Fast: The Clinical Question : www.med.yale.edu/library/education/guides/screencasts/finditfast/finditfast_2/
Acquire

24. Levels of Evidence
for Therapy Question
Level of Evidence Type of Study
1a Systematic reviews of randomized controlled trials
(RCTs)
1b Individual RCTs with narrow confidence interval
2a Systematic reviews of cohort studies
2b Individual cohort studies and low-quality RCTs
3a Systematic reviews of case-control studies
3b Case-control studies
4 Case series and poor quality cohort and case-control
studies
5 Expert opinion
Levels of evidence (2001). Centre for Evidence Based Medicine. Retrieved 26 Aug 2008 from
http://www.cebm.net/index.aspx?o=1025
Acquire
24

25. Filtered vs Unfiltered Information Sources
Less time 1a - SRs of
Less work RCTs
Less evidence
Summaries
Filtered
1b 1b
2b 2a 2b 2a
Unfiltered
More time
3b 3b
More work 4 4 5
5
More evidence
Acquire

26. Filtered
Unfiltered
Expert Opinion
Acquire

27. Summary

28. EBM Process
Formulating
Evaluating the clinical
? ?
the Process question
Your patient for whom
you are uncertain about
therapy, diagnosis, or Searching
Incorporating prognosis the Evidence
evidence into
decision-making ?
?
?
Appraising
the Evidence

29. What kind of question is this:
What causes jaundice?
A. Background
B. Etiology
C. Foreground
D. PICO

30. What is the “O” in this question:
When should fibreoptic phototherapy be initiated to
prevent brain damage for a jaundiced newborn?
A. Fibreoptic phototherapy
B. Jaundiced newborn
C. Prevent brain damage

31. Which of the following is the best source of
evidence to answer the question:
In jaundiced infants, is single volume exchange
transfusion superior to double volume exchange?
A. Case series
B. Cohort study
C. Diagnostic validation study
D. RCT