The document provides an overview of evidence-based medicine, including what it is, why it is important, where evidence comes from, levels of evidence, and the steps to practice evidence-based medicine. It discusses formulating a clear clinical question, searching for relevant information and studies, critically appraising the evidence, and applying the evidence to a specific patient case. Key aspects covered include evaluating the validity, importance, and applicability of various types of studies to determine the strength and relevance of the evidence. The goal is to systematically review and apply the best available research findings to clinical decision making.

1. Evidence Based Medicine:
Evaluating and translating evidence
into clinical practice
Francisco Javier Rodríguez-Vera
Department of Internal Medicine
Hospital do Barlavento Algarvio
Portimão
Portugal. EU

2. Evidence Based Medicine: What it
is?
Main Entry: 1ev·i·dence
Pronunciation: 'e-v&-d&n(t)s, -v&-"den(t)s
Function: noun
1 a : an outward sign : INDICATION b : something that furnishes proof :
TESTIMONY; specifically : something legally submitted to a tribunal to
ascertain the truth of a matter
2 : one who bears witness; especially : one who voluntarily confesses a crime
and testifies for the prosecution against his accomplices

3. “Is the process of systematically reviewing,
appraising and using clinical research findings to aid
the delivery of optimum clinical care to patients”
Rosenberg W, Donald A. Evidence-based Medicine: an approach to clinical
problem solving. BMJ 1995; 310 (6987):1122-1126
Consists in decision making according the
state of the art of the medical knowledge

4. Evidence Based Medicine: Why?

10. Evidence Based Medicine: Why?

11. Is a tool for the efficient management
of the knowledge

12. Evidence Based Medicine

13. Where is evidence?

14. Reasoning and intuition
Published evidence
Colleagues
Personal experience
Bottom drawer

16. Where is evidence?
Personal experience
Reasoning and intuition
Colleagues
Bottom drawer (pieces of paper in the office)
Published evidence

17. Levels of evidence
I. Strong evidence from at least one systematic review of
multiple well designed randomised controlled trials.
II. Strong evidence from at least one properly designed
randomised controlled trial of appropriate size.
III. Evidence from well designed trials such as non-randomised
trials, cohort studies, time series matched case-
controlled studies.
IV. Evidence from well-designed non-experimental studies
from more than one centre or research group.
V. Opinions of respected authorities, based on clinical
evidence, descriptive studies or reports of expert
committees.

18. -
systematic review
+
randomised controlled trial
Number of Level of
studies evidence
non-randomised trials, cohort
-
studies, time series matched
+
case-controlled studies.
non-experimental studies
Opinions

19. How to do Evidence Based Medicine. Steps.
1. Elaboration of a clinical question
2. Searching the information
3. Critical appraise.
4. Application to our case

20. How to make a clinical question.
Questions in Evidence Based Medicine will have to be
made in clear and well defined terms:
oPerson or population in question
oIntervention given
oComparison (if appropriate)
oOutcomes considered
The best question is that which can be answered with
Yes or No

21. Patient or Problem Intervention Comparison Intervention Outcome
Description of the patient or the Could Relevant most often when looking Clinical outcome of interest to
target disorder of interest include: at therapy questions you and your patient
•Exposure
•Diagnostic
test
•Prognostic
factor
•Therapy
•Patient
perception
etc.

22. Questions
Therapy
Prognosis
Diagnosis
Harm/Etiology

23. Therapy
You admit a 65 year old man with a stroke. On examination
you find that he has mild weakness of the right arm and
right leg and bilateral carotid bruits. You send the patient
for carotid doppler ultrasonography and subsequently
receive the report that he has moderate stenosis (50-69%
by NASCET criteria) of the ipsilateral carotid artery. You
want to now if aspirin will be indicated in this patient.

24. Can ASA decrease the risk of stroke?

25. Patient or Problem Intervention Comparison Intervention Outcome
65 year old man with a stroke and moderate carotid stenosis ASA Placebo Stroke

26. In a 65 year old man with a stroke and moderate
carotid stenosis, can ASA decrease the risk of another
stroke compared with no treatment?

27. Prognosis
You see a 70 year old man in your outpatient clinic 3 months
after he was discharged from your service with an ischemic
stroke. He is in sinus rhythm, has mild residual left-sided
weakness but is otherwise well. His only medication is ASA
and he has no allergies. He recently saw an article on the
BMJ website describing the risk of seizure after a stroke and
is concerned that this will happen to him.

28. Patient or Problem 70 year old man
Intervention Stroke
Comparison Intervention
Outcome Seizure
Question In a 70 year old man does a history of stroke increase his risk for seizure?
In a 70 year old man does a history of stroke increase his
risk for seizure?

29. Diagnosis
You admit a 75 year old woman with community-acquired
pneumonia. She responds nicely to appropriate antibiotics
but her hemoglobin remains at 10 g/dl with an MCV of 80.
Her peripheral blood smear shows hypochromia, she is
otherwise well and is on no incriminating medications. You
contact her family physician and find out that her Hgb was
10.5 g/dl 6 months ago. She has never been investigated
for anaemia. A ferritin has been ordered and comes back
at 10 mmol/l. You admit to yourself that you're unsure
how to interpret a ferritin result and aren't sure how
precise and accurate it is.

30. Patient or Problem Elderly woman with anaemia
Intervention Ferritin
Outcome Iron deficiency anaemia
Question In an elderly woman with hypochromic, microcytic anaemia, can a low ferritin
diagnose iron deficiency anaemia?
In an elderly woman with hypochromic, microcytic anaemia,
can a low ferritin diagnose iron deficiency anaemia?

31. Harm/Etiology
You see a 50 year old man who asks for a repeat
prescription of sotalol which he has been taking for
extrasystoles for several years. He has a remote history
of an MI. You haven't seen him previously and are
concerned about the proarrhythmic properties of sotalol
given what is known about other antiarrhythmics.

32. Patient or Problem Man with extrasystoles
Intervention Sotalol
Compar Intervention Placebo
Outcome Death
Question In a man with extrasystoles and a remote history of MI, does treatment with sotalol increase his risk of death?
In a man with extrasystoles and a remote history
of MI, does treatment with sotalol increase his
risk of death?

35. How to do Evidence Based Medicine. Steps.
1. Elaboration of a clinical question
2. Searching the information
3. Critical appraise.
4. Application to our case

36. Searching the information
• Background Resources:
• Give overview of a topic; print textbooks,
electronic textbooks, narrative reviews in journals
1. Harrison’s Online
2. Scientific American Medicine Online
3. MD Consult
4. Medline (for narrative review articles)
a. Ovid
b. PubMed

37. •Foreground Resources: (reports of original research or
abstracts, summaries, syntheses of primary research)
• Secondary Sources-abstracts, summaries and syntheses
of original research
1. Cochrane Database of Systematic Reviews- systematic
review of a topic
•2. ACP Journal Club- review and commentary of an
article
•3. Clinical Evidence - summarizes evidence available for
common clinical questions-includes Cochrane and ACP
Journal Club report (direct)
4. Practice Guidelines

38. • Primary Sources-reports of original research
1. OVID Medline
2. PubMed Medline

39. It indexes nearly 9 million records representing
articles from more than 3,600 biomedical
journals published world-wide.
http://www.pubmed.org
includes the full text of the regularly
updated systematic reviews of the effects of
healthcare interventions (therapy) prepared
by The Cochrane Collaboration.
http://www.cochrane.org

41. PubMed
Created for the National Library of Medicine
Three forms of presentation:
Full text (links to the journal)
Abstracts (papers and original articles)
Title and Authors (Letters to editor)

42. PubMed. Advantages and inconvenients
It accumulates the most Publications not
relevant journals included: grey
literature
Free
Requires learning
Updated
Full text not avalaible
in all pubblications

43. PubMed: an example of a search
We want to know what´s the state of the art of the
treatment of a myocardial infarction
"Myocardial Infarction/therapy"[MeSH]: 37326 arts
Limits: arts with abstract: 20310 arts
Add limit Clinical Meta-analysis: 167 arts
change limit: clinical practise guideline: 23 arts
Written in English and published in the last year: 4 arts

44. Evidence Based medicine: After the
efficient search
Depending the subject a search may give from 5
to 500 entries.
Reading of abstracts and elimination of articles
“After reading abstracts the search was limited
to…”
Reading of articles in full text
“After the reading in full text, the search
was limited to….articles”

45. The problem of obtaining articles
How would i get a full text article?
Official site of the journal
Accumulators
Asking the author for a copy of the article
Sites with passwords to fulltext

46. Some articles are avalaible full text for free

47. http://intl.highwire.org/
http://ebro3.unizar.es:8080/rev/default.html

48. “Dear Dr …
I´m researching on…., and in a search in PubMed I
found the abstract of your study published in…, which I
found extremely interesting. I would be pleased if you
could provide my with a separata of your article.
Sincerely yours…”

49. Now, we have articles that may give an
answer to our clinical question
Are these articles reliable?

50. I. Level of evidence provided by the
article
II.Possibility of bias (internal
coherence) of the article

51. Levels of evidence
-
systematic review
+
randomised controlled trial
Number of Level of
studies evidence
non-randomised trials, cohort
-
studies, time series matched
+
case-controlled studies.
non-experimental studies
Opinions

53. Internal Coherence: The critical appraisal
-Consists in determining the possibility of bias of
the study.
-checklists

54. Critical appraisal. general
-Are the groups similar (homogeneity)?
-Did it exist randomization?was it described?
-Are the endpoints clearly defined?
-Is the statistical study correct?
-Are the conclusions according with the
results?
-Are the results of this study appliable to my
patient(s)?

55. Critical appraisal. Review/Metanalysis
Are the results valid?
1. Did the review address a clearly focused issue?
2. Did the review describe:
 the population studied?
 the intervention given?
 the outcomes considered?

56. Critical appraisal. Review
2. Did the authors select the right sort of studies for the
review?
The right studies would:
address the review's question
 have an adequate study design

57. Critical appraisal. Review
3. Do you think the important, relevant studies were
included?
Look for:
 which bibliographic databases were used
 personal contact with experts
 search for unpublished as well as published studies
 search for non-English language studies

58. Critical appraisal. Review
4. Did the review's authors do enough to assess the
quality of the included studies?
Did they use:
description of randomization?
 rating scale?

59. Critical appraisal. Review
What are the results?
5. Were the results similar from study to study?
 Are the results of all the included studies clearly
displayed?
 Are the results from different studies similar?
 If not, are the reasons for variations between studies
discussed?

60. Critical appraisal. Review
6. What is the overall result of the review?
Is there a clinical bottom-line?
What is it?
What is the numerical result?

61. Critical appraisal. Review
7. How precise are the results?
Is there a confidence interval?

62. Critical appraisal. Review
Can I use the results to help my patient?
8. Can I apply the results to my patient?
Is this patient so different from those in the trial that
the results don’t apply?

63. Critical appraisal. Review
9. Should I apply the results to my patient?
how great would the benefit of therapy be for this
particular patient?
 Is the intervention consistent with my patient's values and
preferences?
 Were all the clinically important outcomes considered?
 Are the benefits worth the harms and costs?

64. Critical appraisal. Treatment.
Is the research valid?
1a. Was the assignment of patients to treatments randomized?
1b. Was the randomization list concealed?
1c. Were subjects and clinicians ‘blind’ to which treatment was
being received?

65. Critical appraisal. Treatment.
2a. Were all subjects who entered the trial accounted for at
its conclusion?
2b. Were they analyzed in the groups to which they were
randomized?

66. Critical appraisal. Treatment.
3a. Aside from the experimental treatment, were
the groups treated equally?
3b. Were the groups similar at the start of the
trial?

67. Critical appraisal. Treatment.
Is the research important?
RRR (Relative risk reduction)
ARR (Absolute risk reduction)
NNT (Number needed to treat)

68. Critical appraisal. Treatment.
Can I apply it to my patient?
4. Is this patient so different from those in the trial
that the results don’t apply?

69. Critical appraisal. Treatment.
5a. How great would the benefit of therapy be for this
particular patient?
5b. What is the event rate in my practice for patients like
this one?

70. Critical appraisal. Treatment.
Is it consistent with the patients values and
preferences?
6. Do I have a clear assessment of the patient’s values
and preferences?

71. Critical appraisal. Treatment.
7. Do this intervention and its potential consequences
meet them?

72. Critical appraisal. Diagnosis
Is the research valid?
1. Was there an independent, blind comparison with a
reference ("gold") standard of diagnosis?

73. Critical appraisal. Diagnosis
2. Was the diagnostic test evaluated in an appropriate
spectrum of patients (like those in whom it would be
used in practice)?

74. Critical appraisal. Diagnosis
3. Was the reference standard applied regardless of the
diagnostic test result?

75. Critical appraisal. Diagnosis
Is the research important?
Sensitivity
Specificity

76. Critical appraisal. Diagnosis
Can I apply it to my patient?
4. Is the diagnostic test available, affordable,
accurate, and precise in your setting?

77. Critical appraisal. Diagnosis
5. Can you generate a clinically sensible estimate of
your patient's pre-test probability (from practice data,
from personal experience, from the report itself, or from
clinical speculation?)

78. Critical appraisal. Diagnosis
6. Will the resulting post-test probabilities affect your
management and help your patient? (Could it move
you across a test-treatment threshold?)

79. Critical appraisal. Prognosis/harm
Is the research valid?
1. Was a defined, representative sample of patients
assembled at a common (usually early) point in the
course of their disease?

80. Critical appraisal. Prognosis/harm
2. Was patient follow-up sufficiently long and
complete?

81. Critical appraisal. Prognosis/harm
3. Were objective outcome criteria applied in a
"blind" fashion?

82. Critical appraisal. Prognosis/harm
4. If subgroups with different prognoses are
identified, was there adjustment for important
prognostic factors?

83. Critical appraisal. Prognosis/harm
5. Was there validation in an independent group
("test-set") of patients?

84. Critical appraisal. Prognosis/harm
Is the research important?
Outcome Rate (95% CI)
Probability (95% CI)

85. Critical appraisal. Prognosis/harm
Can I apply it to my patient?
6. Were the study patients similar to your own?

86. Critical appraisal. Prognosis/harm
7. Will this evidence make a clinically important impact
on your conclusions about what to offer or tell your
patient?

87. After the critical appraisal you
conclude that that article you´ve read
has a low-moderate-high probabilities
to be biased

88. Summary
After you make a clinical question, you
formulate correctly that question, look
for the information , obtain the
appropriate articles and make an
appropriate critical appraisal, you get
the following answer:
“there is a X level of evidence to assure
that the answer to our question was
yes/no”

89. frodriguezv14@hotmail.com
frodriguezv@sego.es