introduction to evidence-based medicine
TRANSCRIPT
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Evidence-Based Medicine (EBM)
INDS 301, Jan. 2013Prosanto Chaudhury, MD, MSc, FRCSC, FACSRobin Featherstone, MLIS
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Objectives
By the end of the lecture, you will be able to:1. Describe objectives and expectations for the
course2. Describe the five stages of the EBM process3. Differentiate between background and
foreground questions4. Describe the components of a PICO question5. Categorize PICO questions and identify the best
studies to answer each question type
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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 resourcesSmall group 1 PICO question formationLecture 2 Critical appraisal of randomized controlled trials (RCT) and
systematic reviews (SR)Small group 2 Appraisal of a RCTSmall group 3 Appraisal of a SRSmall group 4 Appraisal of a diagnostic test study
Course website: http://www.jamaevidence.com/
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EvaluationItem Description WeightSmall Groups 4 interactive sessions with clinical tutors.
Evaluation based on participation.40%
Assignment 3 pages including:• Clinical scenario• PICO• Search strategy• Name of chosen paper• Critical appraisal• Your conclusion
30%
OSCE 15 minute station:• Develop a question based on a clinical scenario• Perform a search based on your question
30%
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Introduction to EBM
Why are we doing this?
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Why is EBM important?
“Evidence-based medicine is the integration of best research evidence with clinical expertise and patient values”
- Dave Sackett
Clinical Expertise
Best research evidence
Patient Concerns
EBM
Slide courtesy Prof Paul Glasziou, CEBM
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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
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Challenges to practicing EBM
1960 1970 1980 1990 2000 20100
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RCTs published over the last 50 years
RCTs
Source: PubMed data for "randomized controlled trial"[Publication Type]
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How I use EBM
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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)
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EBM Process
Appraising the Evidence
Incorporating evidence into decision-making
Evaluating the Process
Formulating the clinical question
Searching the Evidence
Your patient for whom you are uncertain about therapy, diagnosis, or prognosis
Ask
Acquire
AppraiseApply
Assess
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EBM Question Formation
1. Background vs Foreground
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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.
[1.]
What is pancytopenia?
What is the diagnostic test for meningitis?
Can a 70 year old pancytopenic patient with suspected meningitis receive platelets before undergoing a lumbar puncture?
Ask
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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 Hodgkin’s lymphoma?
For a 25 year old female with stage IIA Hodgkin’s lymphoma, is combined modality therapy superior to chemotherapy alone?
Ask
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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.
Creative copyright image. Attribution: James Heilman, MD. Accessed from http://upload.wikimedia.org/wikipedia/commons/0/0a/DVT2010.JPG
Discuss with your neighbour. Record one background and one foreground question.
Ask
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[1.]
Sources for Background Questions (AKA “Filtered Information”)• Textbooks• Handbooks• Manuals• etc
Background Questions
Acquire
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EBM Question Formation
2. P.I.C.O.Patient, Population, or ProblemIntervention or exposureComparisonOutcome
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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
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SimplePatient, Population, or Problem
Patients with common warts
Intervention or exposure
Duct tape
Comparison Cryotherapy
Outcome Eliminating warts
Answerable clinical question:
In patients with common warts, is duct tape as effective as cryotherapy in eliminating warts?
Ask
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Intermediate
Ask
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.
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IntermediatePatient, Population, or Problem
Newborns with suspected immune thrombocytopenia
Intervention or exposure
Blood test to check platelets
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
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Best studies to answer each question type
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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 studiesTherapy • Systematic review of Randomized Controlled
Trials (RCTs)• Single RCT
1 Heneghan, Carl, and Douglas Badenoch. Evidence-Based Medicine Toolkit. 2nd ed. Malden, Mass.: BMJ Books/Blackwell Pub., 2006.2 Glover, Jan, and Lei Wang. Find it Fast: The Clinical Question : www.med.yale.edu/library/education/guides/screencasts/finditfast/finditfast_2/ Acquire
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Levels of Evidencefor Therapy Question
Level of Evidence Type of Study
1a Systematic reviews of randomized controlled trials (RCTs)
1b Individual RCTs with narrow confidence interval2a Systematic reviews of cohort studies2b Individual cohort studies and low-quality RCTs3a Systematic reviews of case-control studies3b Case-control studies4 Case series and poor quality cohort and case-control
studies5 Expert opinion
24Levels of evidence (2001). Centre for Evidence Based Medicine. Retrieved 26 Aug 2008 from http://www.cebm.net/index.aspx?o=1025 Acquire
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Unfiltered
Filtered
2a 2b
543b
4
1b1b
2a
5
2b
3b
Summaries
Filtered vs Unfiltered Information Sources
1a - SRs of RCTs
Acquire
More timeMore workMore evidence
Less timeLess workLess evidence
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Unfiltered
Expert Opinion
Filtered
Acquire
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Summary
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EBM Process
Appraising the Evidence
Incorporating evidence into decision-making
Evaluating the Process
Formulating the clinical question
Searching the Evidence
Your patient for whom you are uncertain about therapy, diagnosis, or prognosis
?
?
??
?
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What kind of question is this:
What causes jaundice?
A. BackgroundB. EtiologyC. ForegroundD. PICO
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What is the “O” in this question:
When should fibreoptic phototherapy be initiated to prevent brain damage for a jaundiced newborn?
A. Fibreoptic phototherapyB. Jaundiced newbornC. Prevent brain damage
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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 seriesB. Cohort studyC. Diagnostic validation studyD. RCT