Evidence-Based Practice Lecture 2

2. The Culture of Health Care
Evidence-Based Practice
Lecture b
This material (Comp 2 Unit 5) was developed by Oregon Health & Science University, funded by the Department
of Health and Human Services, Office of the National Coordinator for Health Information Technology under
Award Number IU24OC000015. This material was updated in 2016 by Bellevue College under Award
Number 90WT0002.
This work is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International
License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-sa/4.0/.

3. Evidence-Based Practice
Learning Objectives
• Define the key tenets of evidence-based medicine (EBM) and its
role in the culture of health care (Lectures a, b).
• Construct answerable clinical questions and critically appraise
evidence answering them (Lecture b).
• Explain how EBM can be applied to intervention studies, including
the phrasing of answerable questions, finding evidence to answer
them, and applying them to given clinical situations (Lecture c).
• Describe how EBM can be applied to key clinical questions of
diagnosis, harm, and prognosis (Lectures d, e).
• Discuss the benefits and limitations to summarizing evidence
(Lecture f).
• Describe how EBM is used in clinical settings through clinical
practice guidelines and decision analysis (Lecture g).
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4. Making Evidence-Based Clinical
Decisions (Mulrow, 1997)
5.1 Figure: Adapted from Mulrow, Cook, &
Davidoff, 1997 4

5. Best Resources for EBM
• Three major books:
– Evidence-Based Medicine: How to Practice and Teach It, 4th edition,
Straus, Richardson, Glasziou, and Haynes (2010)
o Informally known as the “Sackett Book” for original author David Sackett
– Users’ Guides to the Medical Literature: A Manual for Evidence-Based
Clinical Practice, 3rd edition, Guyatt, Rennie, Meade, and Cook (2015)
o Encyclopedic guide to principles and applications of EBM
– Users’ Guides to the Medical Literature: Essentials of Evidence-Based
Clinical Practice, 3rd edition, Guyatt, Rennie, Meade, and Cook (2015)
o Handbook of the most clinically relevant content of the larger manual
• Web sites:
– Centre for Evidence-based Medicine: http://www.cebm.net
– Centre for Health Evidence: http://www.cche.net
– http://www.nettingtheevidence.org.uk
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6. The Changing Nature of EBM
(Hersh, 1999)
• Initial approach ( “first generation”) was for
clinician to find and critically appraise evidence
– Too time consuming; clinicians lack expertise
• More recent approach ( “next generation”) is
synthesis and synopsis of evidence for clinician
– Access to online, up-to-date information makes easier
• Slawson & Shaughnessy (2005) argue for more
emphasis on teaching information management
(seeking) than on techniques of EBM
6

7. Another Viewpoint Concerning
Evidence (Haynes, 1999)
• Can it work?
– Efficacy studies take place under “ideal” circumstances
– This unit looks mainly at such studies
• Does it work?
– Effectiveness studies ascertain whether something works
in the “real world”
– Sometimes called “outcomes research” (Clancy &
Eisenberg, 1998)
• Is it worth it?
– Cost-benefit or cost-effectiveness studies determine
whether benefits worthwhile in relation to cost or other
resources
7

8. Hierarchy of Evidence—The 4S
Model (Haynes, 2001)
Subsequently updated to 5S
(Haynes, 2005) and 6S
(DiCenso, 2009) models,
but 4S is preferred
5.2 Figure: adapted from Haynes’s “4S” model of the Hierarchy of Evidence, 2001
8

9. Where the Evidence Comes From
5.3 Figure: Adapted from Haynes’s “S4” model of the Hierarchy of Evidence, 2001 with types and sources of evidence
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10. Studies
• Accessed (usually) in literature databases
such as Medline
– Most common and freely available system for
accessing medical literature is PubMed, available
at http://pubmed.gov
• Retrieved from journals
– Many now available electronically
• Application of critical appraisal and formulas
– For example, relative risk, number needed to
treat, sensitivity, odds ratio
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11. Syntheses
• Systematic reviews
– Exhaustive, systematic review of data on a topic
o Not a simple literature review or overview of papers
one knows about
– Application, where appropriate, of meta-analysis,
the combination of results from multiple studies in
a single analysis
o Studies must be appropriately similar, and there are
methodological means to assess that
– Available in PubMed or in specialized Pubmed
Health http://www.ncbi.nlm.nih.gov/pubmedhealth
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12. Synopses and Systems
• Synopses—Highly summarized information
appropriate for clinical setting, such as
– Critically appraised topics (CATs)
– Clinical Evidence, InfoPOEMS, PIER
– Clinical practice guidelines
• Systems—Decision support within electronic
health record systems
– Best way to provide evidence to clinicians at point
of clinical decision making
12

13. Overview of the Application of EBM
• Steps include
– Phrasing a clinical question that is pertinent
and answerable
– Identifying evidence to address the question
– Critically appraising the evidence to determine
whether it applies to the patient
13

14. Phrasing the Clinical Question
• Background vs. foreground questions
– Background questions ask for general
knowledge about a disorder
o Usually answered with textbooks and classical
review articles
– Foreground questions ask for knowledge
about managing patients with a disorder
o Usually answered using EBM techniques
14

15. Background Questions
• General information not specific to a given
patient
• Examples
– What causes pneumonia?
– When do complications of type I diabetes usually
occur?
• Distinction from foreground questions can be
blurry
– New etiologies of disease
– Level of training (e.g., specialist vs. student)
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16. Foreground Questions
• Have three or four essential components
(PICO)
– Patient and/or problem
– Intervention
– Comparison intervention (if appropriate)
– Outcomes
• Example
– In an elderly patient with congestive heart failure,
are beta blockers helpful in reducing morbidity
and mortality without excess side effects?
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17. Four Categories of Foreground
Questions
• Intervention (or therapy)—Benefit of
treatment or prevention
• Diagnosis—Test diagnosing disease
• Harm—Etiology or cause of disease
• Prognosis—Outcome of disease course
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18. Questions to Ask about the Results
from Any Study
• Are the results valid?
• Are the results important?
• Can the results be applied to patient care?
Specific sub-questions depend on type of
question and study
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19. Evidence-Based Practice
Summary – Lecture b
• There are many easily accessible resources for
EBM
• Approach has changed over the years
• Can be best viewed from the 4S model
demonstrating the hierarchy of evidence, based
on a foundation of studies, brought together
where possible by syntheses, summarized in
synopses, and implemented in systems that
make it actionable
• When seeking evidence, it is critical to
appropriately phrase the clinical question 19

20. Evidence-Based Practice
References – Lecture b
References
Centre for Evidence-Based Medicine. (n.d.). Retrieved from http://www.cebm.net
Centre for Health Evidence. (n.d.). Retrieved from http://www.cche.net
Clancy, C., & Eisenberg, J. (1998). Outcomes research: Measuring the end results of health care.
Science, 282, 245–246.
DiCenso, A., Bayley, L., & Haynes, R. (2009). ACP Journal Club. Editorial: Accessing preappraised
evidence: Fine-tuning the 5S model into a 6S model. Annals of Internal Medicine, 151(6), JC3-2,
JC3-3.
Netting the Evidence. (2009, November 11). [Web blog]. Evidence-based medicine. Retrieved from
http://www.nettingtheevidence.org.uk
Guyatt, G., et al. (2015). Users’ guides to the medical literature: A manual for evidence-based clinical
practice, 3rd ed. American Medical Association
Guyatt, G., et al. (2015). Users' guides to the medical literature: Essentials of evidence-based clinical
practice, 3rd ed. New York: McGraw-Hill.
Haynes, R. (1999). Can it work? Does it work? Is it worth it? British Medical Journal, 319, 652–653.
Haynes, R. (2001). Of studies, syntheses, synopses, and systems: The "4S" evolution of services for
finding current best evidence. ACP Journal Club, 134, A11–A13.
Haynes, R. (2006). Of studies, syntheses, synopses, summaries, and systems: The "5S" evolution of
information services for evidence-based healthcare decisions. Evidence-Based Medicine, 11,
162–164.
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21. Evidence-Based Practice
References – Lecture b Continued
References
Hersch, W. (2009). Information retrieval: A health and biomedical perspective. New York: Springer
Verlag.
Mulrow, C., Cook, D., & Davidoff, F. (1997). Systematic reviews: Critical links in the great chain of
evidence. Annals of Internal Medicine, 126, 389–391.
Slawson, D., & Shaughnessy, A. (2005). Teaching evidence-based medicine: Should we be teaching
information management instead? Academic Medicine, 80, 685–689.
Straus, S., & Glasziou, P. (2011). Evidence-based medicine: How to practice and teach it, 4th edition.
Edinburgh: Elsevier Churchill Livingstone.
U.S. National Library of Medicine. (n.d.). PubMed Health. For Researchers. Retrieved from
https://www.ncbi.nlm.nih.gov/pubmedhealth/researchers/
U.S. National Library of Medicine. (n.d.). PubMed. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed
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22. Evidence-Based Practice
References – Lecture b Continued 2
Charts, Tables, Figures
5.1 Figure: Adapted from Mulrow, C., Cook, D., & Davidoff, F. (1997). Systematic reviews: Critical
links in the great chain of evidence. Annals of Internal Medicine, 126, 389–391.
5.2 Figure: Adapted from Haynes’s “4S” model of the Hierarchy of Evidence: Haynes, R. (2001). Of
studies, syntheses, synopses, and systems: The "4S" evolution of services for finding current best
evidence. ACP Journal Club, 134, A11–A13.
5.3 Figure: Adapted from Haynes’s “4S” model of the Hierarchy of Evidence with types and sources of
evidence: Haynes, R. (2001). Of studies, syntheses, synopses, and systems: The "4S" evolution of
services for finding current best evidence. ACP Journal Club, 134, A11–A13.
22

23. The Culture of Health Care
Evidence-Based Practice
Lecture b
This material was developed by Oregon Health &
Science University, funded by the Department of
Health and Human Services, Office of the National
Coordinator for Health Information Technology
under Award Number IU24OC000015. This
material was updated in 2016 by Bellevue College
under Award Number 90WT0002.
23