Introduction to Evidence-Based Medicine

Evidence-Based Medicine (EBM)

INDS 301, Jan. 2013Prosanto Chaudhury, MD, MSc, FRCSC, FACSRobin Featherstone, MLIS

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

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/

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%

Introduction to EBM

Why are we doing this?

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

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

Challenges to practicing EBM

1960 1970 1980 1990 2000 20100

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12000

14000

16000

18000

20000

RCTs published over the last 50 years

RCTs

Source: PubMed data for "randomized controlled trial"[Publication Type]

How I use EBM

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)

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

EBM Question Formation

1. Background vs Foreground

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

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

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

[1.]

Sources for Background Questions (AKA “Filtered Information”)• Textbooks• Handbooks• Manuals• etc

Background Questions

Acquire

EBM Question Formation

2. P.I.C.O.Patient, Population, or ProblemIntervention or exposureComparisonOutcome

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

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

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.

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

Best studies to answer each question type

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

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

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

Unfiltered

Expert Opinion

Filtered

Acquire

Summary

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

?

?

??

?

What kind of question is this:

What causes jaundice?

A. BackgroundB. EtiologyC. ForegroundD. PICO

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

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